I just spent a few minutes putting together this comparison of the new Arno Pro typeface with a few other serifed typefaces I favor. Click on the image for a larger version; it makes some of the differences a little clearer. I probably should have included Adobe's Garamond Premier Pro too. Palatino is nice too, but I don't really have a proper set.
All of them are at displayed at the 12pt optical size. Arno almost seems like it is perhaps a design somewhere in between Minion and Jenson, at least when considering the serifs and terminals. I am also somewhat surprised by how much more compact Arno appears at the same point size. It is a pre-release version, so it could be that it has not yet received some final tweaking. In any event, it should hopefully be obvious that the first three typefaces are more closely related than Warnock is to any of them, with its very sharp and angular serifs and terminals.
At the moment, I think I am leaning toward Jenson for my dissertation, but I'll probably change my mind several times until I compare a more completed product. I've been thinking a little more about the design of Gentzen lately. I'm going to try to find time to at least do an initial design for the turnstyle and perhaps the universal quantifier this weekend.