Could you clarify what you mean by abiding and non-abiding?
I've heard it said that Theravada is a cosmic suicide club... that the goal is complete cessation of existence. Is that what is meant by non-abiding?
Abiding essentially means permanent... perfect buddhahood. Non-abiding would be an experience of liberation which would have lasting effects and implications, but in time afflicted perception would eventually creep back in. But even within the tenets of buddhahood there are certain attributes which distinguish the nature of that buddhahood; within Dzogchen for example there is buddhahood that reverts to the cause and buddhahood which doesn't revert to the cause... among many other differences.
.....But....there are two kinds of buddhahood discussed in Dzogchen; buddhahood that reverts to the cause and the buddhahood that does not revert the cause.
Those whose buddhahood was incomplete can still fall into sentient being hood if they do not recognize the arising of the basis as being their own display......
There are, if you recall, three stages of Buddhahood. Since the first two stages of Buddhahood do not realized all phenomena as the display of their own wisdom, the eleventh and twelfth bhumi are not complete buddhahood, this true even in Sarma schools.
There are two ways these things are explained, the common way, which accords with lower vehicles, in which the basis and the result are more or less the same.
Then there is the uncommon way Dzogchen explains these things, in which the basis and the result are different from that of the lower vehicles.
For example, in general, the nine yānas approach is to assert that all-basis is dharmakāya. In the special Dzogchen view, asserting that dharmakāya is the ālaya is a "Buddhist deviation". In Dzogchen, the ālaya is, as stated in the Mind Tantra of Vajrasattva:
'The all-basis is the bardo of everything,
unconsciousness, unclear, and inexpressible.'
The example for the ālaya is space. The example for the dharmakāya is celestial bodies.
So you see, it is really not so simple as proclaiming that the basis and the result are the same for all schools, only the result differs.
For example, the Samputa maintains there is a distinct different in omniscience between an eleventh and twelfth stage buddha, and a thirteenth stage Buddha. Related to this, Dzogchen refers to the 13-16 bhumis as those that "dwell in wisdom". Why? Because only 13th stage Vajradhara's on up understand that all appearances are the display of their own wisdom.
Most people think that Buddhahood is irreversible; Dzogchen on the other hand asserts that the buddhahood of the lower yanas is reverts into the basis, and only Dzogchen results in complete and irreversible buddhahood.
These are the kinds of things you discover when you read Vima Nyingthig, Khandro Nyingthig, Gongpa Zangthal, the Seventeen tantras and so on.
The later in Tibetan history you go, the more homogenized the presentation of the four schools becomes. When you exam the texts of the Pre-Sarma period, then you find Dzogchen is really very different from what was introduced from India during the time of Rinchen Zangpo onwards.
Dzogchen did not spread widely in India, neither did anuyoga. The main tantric teaching of India was Yoga Tantra/Mahayoga.
Many masters to not present whole picture of Dzogchen. HHDL's agenda, which I respect, is to bring harmony to all schools.
My interest is a little different -- I am interested in what makes Dzogchen so unique and so powerful. I know the difference between what is commonly stated as a nice political thing so Sakyas, Gelugpas and Sarma-oriented Kagyus don't feel bad, and what the real teachings of Dzogchen say, but are not so publicized. I don't owe allegiance to any school. My interest these days in particular is solely anuyoga and Dzogchen teachings.
That being said, don't think that I consider Lamdre, etc., as lacking depth, efficacy, or profundity -- they are profound, interesting, and wonderful teachings. I just think Dzogchen is more profound, more efficacious, and deeper. This is just my opinion.
It is because buddhahood of lower yānas is incomplete and does not reach the stage of ka dag chen po, great original purity. The simplest way to explain it is that after the this universe dissolves and the next one arises, those beings who have not achieved the stage of ka dag chen po start all over.
Regarding Theravāda, it isn't like that at all... it's just the most traditional form of buddhism, Theravāda literally translates to "the Teaching of the Elders" or "the Ancient Teaching," and is sometimes referred to as Hīnayāna which translates to "Inferior Vehicle", "Deficient Vehicle", the "Abandoned Vehicle", or the "Defective Vehicle" however the term Hīnayāna isn't very endearing, and though widely used, is considered improper. In Theravāda they practice according to the original sutras attributed to Śākyamuni Buddha and in their realization is for them alone which makes them pratyekabuddhas. Some claim that the pratyekas realization is equivalent to that of a bodhisattva, the difference being that a bodhisattva works for the liberation of all sentient beings. Others however say that in order to even achieve proper buddhahood one must abide by the bodhisattva ideal of working for the benefit of all beings, and therefore they denounce the pratyekabuddha's realization as inferior. The sister forum of dharmawheel is http://www.dhammawheel.com
which is pretty much exclusively Theravāda I believe. You can find some good information there regarding that vehicle and it's tenets.
The goal of most vehicles can be said to be aiming at a glimpse of cessation and/or total cessation. However the cessation is the cessation of ignorance which arises from identifying with a personalized view of reality. The fact that we take ourselves to be individuals who were born, exist in time and eventually die is ignorance(avidyā) according to buddhism. The proliferation and evolution of ignorance is the cycle of samsara, and the Dharma is the method to transcend samsara, thus reaching nirvana. So while I wouldn't call it a "cessation of existence" per se, it is the cessation of everything which could be considered "you". I suppose the absence of individual 'being' can be perceived/interpreted as some sort of non-existence to those unfamiliar and possibly intimidated by such a notion. But the state of cessation is in fact your natural and true state of being, beyond birth and death... abiding in this state is buddhahood a.k.a. wisdom(vidyā). That state is beyond the 4 extremes which are (i)existence, (ii) non-existence, (iii) both existence and non-existence, (iv) neither existence nor non-existence.