P1. If something has moral-value giving properties, then it has at least some moral value
P2. The capacity to suffer and experience wellbeing is a moral-value giving property
P3. Sentient animals have the capacity to suffer and experience wellbeing
C Sentient animals have at least some moral value
So it's a bit of a fail that the first argument isn't valid. If it was it would still be trivial without the second component. Or maybe people are more awful than I think.
On to the second argument. To me it isn't obvious that it holds any additional merit over AMC even if it's valid (and it has a lot of problems compared to AMC). P2 is highly contentious; would we really not accept expoiting humans for say medical research if they had an extremely limited sentience? I reject that entirely. I would absolutely accept being used for medical research if my sentience was reduced significantly enough. If the worst suffering I could experience is comparable to being ever so slightly hungry and the highest wellbeing I could experience is comparable to some minor trivial thing, then surely using me for hiv-research and potentially saving millions and millions of lives is warranted. Deontology be damned.
Any potential merit NTT would have over AMC if valid is that it plays around with hypothetical humans and so it's stronger, but that could just as well be seen as a weakness. It's not at all obvious that we would grant moral value to a human with an extremely limited sentience. The whole argument rests on ambiguity/failure of imagination as far as I can tell. What exactly would it entail to be "turned into a cow" (what it's like to be a bat)? Here the argument rests on the person imagining themself "as a cow", which of course is impossible so one does the next best thing: one imagines oneself as oneself minus some stuff + looking like a cow. Well... that doesn't really cut it. And it goes on like that really; what exactly would it mean to "accept if aliens wanted to kill you for food"? Accepting that it wouldn't be immoral isn't the same as accepting one's fate, and it's not obvious that carnists would have a moral problem with aliens killing severely mentally retarded humans for food.
Also: if I'm eating some set A of nutrionally adequate vegan food-items but there's another set B of nutritionally adequate vegan food-items that involve less animals dying and less animal suffering, then am I exploiting animals if I still choose set A? Why would NTT stop with veganism? What's the difference between animals and humans that justifies me eating vegan ice-cream when I don't have to even if it hypothetically involves more animals dying compared to eating the same calories from rice and beans? As far as I can tell Isaac "resolves" this by saying he'd be fine with being killed given that circumstance. So why can't a carnist do the same thing?
AMC avoids all of that. It points to actual humans that we actually grant moral value. As far as I can tell the only really reasonable way to avoid AMC's conclusion is to either argue against species overlap (very difficult, this is basically what Dan Dennett does and even he doesn't really seem to believe it) or to accept that marginal cases don't actually have moral-value giving properties but that they should have rights for some other reason (one could appeal to utilitarianism in the form of social cohesion, that giving these individuals artificial rights serve to secure the actual rights of non-marginal cases more firmly, to the extrinsic value of those individuals etc.)
This isn't to say that NTT is a bad argument, I think its merits can be summed up in the following question (which is the one activists who like NTT seem to actually use): can you point to a difference between animals and humans that would justify treating humans that way if we were in their hooves? Which is basically the golden rule. And fine, if framing a question in some specific way makes people who otherwise wouldn't consider applying the golden rule to non-human animals do so (this question clearly devised as to try and cancel out the speciecism aspect), then that's all for the better.
