Mahayana vs Theravada, crucial differences
My position is of Mahayana the Chinese lineage, selected Sutras I studied, all or parts: Agamas (& some Pali Nikayas), Perfect Enlightenment, Avatamsaka, Surangama, Lotus Sutra, Lankavatara, Saṃdhi-nirmocana-sūtra, Mahayana Parinirvana, Amitāyurdhyāna-sūtra, Diamond Sutra, Platform Sutra, Prajna Paramita (by Kumarajiva), Madhyamaka, Mahisasakas Pratimoksa, Mahāprajñāpāramitāśāstra, Bodhidharma Bloodline Sastra, Samayabhedo-paracanacakra-śāstra, Śariputraparipṛcchā... Path of Liberation (the Pali Vimutti-magga is translated from Chinese) and meditation sutras/abhidharmas, etc.
On Theravada knowledge, parts and/or by scanning/skimming: Nikayas (or from Chinese Agamas), Buddhism SE, almost all the entries on Theravada in Wikipedia incl. its Abhidhamma, Dhammawheel, articles by the Bhikkhus such as Thanissaro, Buddhadasa, Brahm, Bodhi, Sujato, Henepola Gunaratana, Ashin Dr. Nandamalabhivamsa, Walpola Rahula, etc.
1) Mahayana inherits scriptures (excl. Tantra texts) encompassing the Three Turning of Dharma Wheels expounded by the Buddha himself in his 45 years of teaching, i.e., 1st the Agamas, 2nd the Prajna Paramita Sutras, and 3rd the Tathāgatagarbha Sutras. This saying records in almost all the Vinayas and some Sutras such as:
Three Turnings of the Twelve Sections of Dharma Wheels… attained perfect enlightenment for Buddha-hood — Sarvāstivāda Vinaya, translated by Mishu 米殊
Theravada inherits scriptures of the four Nikayas which almost equivalent to the Agamas, however Sutras of the 2nd and 3rd Wheel Turning are missing.
2) Mahayana records in the Agama that the Sutras collected after the gathering of 500 Arhats in the Seven Leaves Cave were written down on white cloth to keep:
Mahakasyapa then selected 40 realized ones among all, relaying from Ananda to have the four Agamas, 1 Madhyama Āgama, 2 Dīrgha Āgama, 3 Ekottara Āgama, 4 Saṃyukta Āgama… each [was written] on 60 rolls of plain cloth. The Bhiksus said, “use these to write in the four scripts (perhaps the Brahmi, Prakrit, Kharoṣṭhī and Armanic scripts), let these be spreading in the world.” …individually writing the 12 sections of the Buddha Sutras, with the Vinayas and Dharmas ready… meeting Maitreya Buddha… for liberation… — Parinirvana Sutra, Agama, translated by Mishu 米殊
According to this plus several Sutras and Mahayana tradition, the four Agamas were spread immediately to lay the foundation, the 2nd and 3rd Turning mainly the Bodhisattvayana/Mahayana Sutras were reserved for approx. 100 years later, waiting until the new generation of disciples matured and Bodhisattva-teachers born to the world after the Buddha's nirvana.
Theravada says writing was not available 2500 years ago and only transmitted by oral recitation. The four or five Nikayas are all that the Buddha taught, nothing more.
3) Mahayana (of the Chinese lineage) preserves Sutras, Vinayas, Sastras and Abhidharmas from all the Early Eighteen Schools. All the scriptures are served as reference instead of presiding over any particular school.
Theravada inherits Suttas and works from the Vibhajyavāda (meant the separatist, a sect active esp. around 300CE teaching different/ newly interpreted doctrines that contradictory to the Early Eighteen Schools). In addition, Theravada its original name was Tambapaṇṇiya (meant Ceylon School), its scriptures and works are from the Mahāvihāravāsins (monks of a monastery in Sri Lanka) only:
The Mahavihara Theravādins of Sri Lanka are descendants of the Sthavira Vibhajyavādins in South India who used the Pali language... — Vibhajyavāda, Wikipedia
4) Mahayana (of the Chinese lineage) receives the scriptures written in Prakrit, Kharoṣṭhī, Gandhari and various Sanskrit scripts, translated to Chinese by Indian Buddhists worked together with the Chinese.
Theravada keeps the scriptures written in Pali, which according to the Theravadins, was close to or same as the Buddha's mother-tongue. However, according to the Chinese sources, that the "Pali" was Sinhalese:
...reciting the Tipitaka, and use Sinhalese to write the scriptures on
leaves, collecting the Tipitaka as the book for the first time... in
500CE, Buddhaghosa studied in Mahavihara of Ceylon, translated the
five Sinhalese Nikayas to Pali and wrote the commentaries. —
1) Mahayana (excl. Tibetan-Buddhism) teaches the 8 consciousnesses, incl. the Tathāgatagarbha-consciousness (如來藏識) or Alaya-vijnana. As quoted the Ekottara Āgama of Sarvastidava stated:
...this is called Alaya. Said, loves Alaya, enjoys Alaya, rejoicing
with Alaya, exhilarating in Alaya
Theravada teaches the 6 consciousnesses. Its consciousness is in an instant arising-ceasing mode. In order to facilitate the gap between the death of consciousness before the arising of the new consciousness its Abhidhamma invented the term Bhavanga, to stitch the two instant moments. It rejects Aalaya-vinnana, though similar sutta found in Pali Anguttara Nikaya (no. 128?):
... the sentient loves aalaya, enjoys aalaya,
rejoicing with aalaya, exhilarating in aalaya
2) Mahayana teaches the intermediate state between death and rebirth. Theravada rejects the intermediate state. However, to answer how can a dead consciousness re-arise again (much like an extinguished fire cannot re-ignite) it puts the Bhavanga to mend the fault.
3) Mahayana teaches the Samyaksaṃbuddha discovered the Dharma that was taught by all previous Buddhas, he also has to receive the "mark" (endorsement or prediction) from previous Buddhas. This designates a world-system can only have one Samyaksaṃbuddha at one time.
Theravada teaches the Sammāsambuddha only required to be self-awaken. It has no difference from a Paccekabuddha in terms of self-awakening except a Paccekabuddha doesn't teach. It is not certain how Theravada ensured multiple Sammāsambuddhas not spontaneously appeared in the world by requiring only self-awakening.
4) Mahayana teaches the Samyaksaṃbuddha with three kayas (bodies), and there are infinite Samyaksaṃbuddhas in the universe with the myriad of world-systems. Theravada teaches only one Sammāsambuddha in the whole world/universe.
5) Mahayana teaches 10 stages of enlightenment. An arhat is equivalent to the 7th stage, who realized Anatman, but still not realized Emptiness. Whilst before the 7th stage are called Bodhisattvas, after the 7th stage called Mahabodhisattvas who mastered the Dharani.
Theravada doesn't have the 10 stages, with arahant as the highest enlightment. It also doesn't have Bodhisattva, only the Buddha before being Buddha was a Bodhisattva.
6) Mahayana teaches great many meditation methods. Though mentioned both in the Agamas/Nikayas, the ānāpānasmṛti, contemplation of foulness/ compassion are different from the Theravada's. Methods are such as White Skeleton, Dharma Door of Hearing, the 25 Doors in Surangama, and 12 meditations in the Perfect Enlightenment... etc. Theravada teaches anapanasati, vipassana and metta-bhavana... etc.
Mahayana scriptures covered all the meditation methods in details the Theravada has few paragraphs on, except the Goenka Vipassana, Mahasi "noting" and abodmen breathing which Mahayana scriptures not covered as that not categorized in the Buddha's teaching.
7) Mahayana the final goal is to attain Buddha-hood, all sentient have the potential to be the Buddha for all have the Tathāgatagarbha. Theravada the final goal is to be an arahant, Buddha-hood is the business for the Buddha only.
8) Mahayana teaches the path to Buddha-hood and one must track the path of a Bodhisattva. The training of a Bodhisattva is to serve all sentient beings, and help them to arrive at liberation. In order to serve, a Bodhisattva must learn and master all worldly skills and resources, this in turn helps to cultivate wisdom. Hence a Bodhisattva doesn't necessary be an ordained Bhiksu but can be in any walk of life.
Theravada the path to liberation is to reach arahantship and then go for nibbana. Hence only being fully ordained can have hope, the laypersons are just worldly followers working for better rebirth.
9) Mahayana accepts Hinayana (arhatship) the beginning stage of the path only, encourages one to reach the graduation that is Buddha-hood and Nirvana.
Theravada takes only the Hinayana goal and graduated as that.
10) Mahayana teaches not eating meat which is an extension of non-killing, following the teacher as the Buddha never ate meat.
Theravada does not teach not to eat meat, but only teaches not to kill by oneself for eating the meat.
11) Mahayana teaches 5 precepts and 6 paramitas. One of the 6 is prajna-paramita (wisdom) therefore Mahayana also engages in metaphysics and philosophical contemplation. However Theravada teaches 5 precepts but not the 6 paramitas therefore often dismisses discussions by citing the poison arrow parable, emphasis is on liberating from suffering.
12) Mahayana teaches the ultimate as Suchness (Tathata), which is a fluid proposition as styled by Nagarjuna's "neither one nor different" (不一不異); it is not nondualism, nor Advaita Vedanta whose founding father Adi Shankara was born in the 8th century, 1000+ years later, making the Buddha copying any ideas from the future is absurd! Theravada teaches that the ultimate is an objective absolute reality, that nibbana is unconditional and nondual - transmundane.