When it comes to level TTs I quite like them all things being equal, but I dislike excessive stickout of stems (or seatposts) even more. So my least favourite is the modern "road" frame with a really short ST, loads of seatpost extension, and a low stack. If you're going to have a low stack just give it a horizontal TT. I know the long seatpost is supposed to give you "suspension" or something but to me it just looks goofy. If I am making a high stack frame I would rather slope the TT to avoid lots of spacers and things up at the front.