Given the recent discussion in the Magellan blog post I thought I'd revive this thread with Elias Capriles' book Sutrayana from the perspective of Dzogchen, available at Scribd. He said:
"The Dzogchen teachings resort to concepts and terms which are extraneous to Prasangika thought, and which are featured in the canonical texts of the Third Promulgation (dharmachakra) and in the philosophical schools based on them, such as the Yogachara School, the Madhyamaka-Swatantrika- Yogachara subschools of Madhyamika thought, and the subschools that make up the inner, subtle Madhyamaka (which are the Zhentongpa and Mahamadhyamaka subschools)" (9).
Also see Sonam Thakchoe's The Two Truths Debate referenced earlier in the thread, as well as his paper "How many truths?" that pre-dates the book. Also Garfield's book Empty Words is available at Scribd.
The following are some excerpts from Empty Words and are points I've made before above and in previous threads. We can see the Yogacara influence in Dzogchen Caprilles admitted above and which is a major sticking point in the shentong/rangtong debate. Similar analysis is found in The Two Truths Debate.
"The fact that all phenomenon are ultimately empty entails very different consequences....for the Madhyamika, it entails that nothing, including emptiness, lacks inherent existence and that all phenomenon are on the same ontological footing. For the Yogacarins, on the other hand, it entails that all objects of consciousness are completely nonexistent and merely imaginary, while the mind itself and the absence of duality are truly existent.... As a consequence, whereas for Nagarjuana the two truths are in the end identical, characterizing the same reality from different perspectives...for Vasubandhu ultimate reality and conventional reality are not in any sense identical.... For Nagarjuna we can express genuine truths through language and can understand reality conceptually. For Vasubandhu neither is possible. Madhyamaka hence provides a non-mystical, immanent characterization of the nature of reality...and of the nature of our knowledge...about one reality. Yogacara epistemology and metaphysics, on the other hand, require for genuine knowledge, for access to truth, a mystical intuition of a transcendent realm.... It hence implicates a strong ontological version of an appearance/reality distinction" (182-3).
"Tsong khapa's own claim [is] that that two truths constitute 'a single ontological identity' with 'different conceptual identities'" (124).
"Go rampa argues...that conventional truth must be eliminated in the ascent to ultimate truth.... The two truths are binary opposites....conventional truth...is the ignorance of ordinary beings....ultimate truth is the sole truth and the phenomenal world is utter illusion" (130-1).
He then shows which people side with which view, and it pretty much comes down to the rangtong (Gelug) versus the shentong (the other Tibetan sects including Dzogchen).