OK - Droid X. Samsung continues to be plagued by a slower update cycle, and the entire series is hit or miss with GPS.
As a user of a phone with a 4.3" screen myself - can't stress this enough - the larger package is worth it for the larger screen.
I like ebooks, use Aldiko (free in the Market) and get my books from Project Gutenberg (all free, have been reading and re-reading all sorts of great stuff). Bigger screen can't be beat.
How about I just go for trilogy and make up for those phantom viewers - get the big screen.
Saw your post in the other thread where you somehow tied easier unlocking on the X to making your Fascinate choice for you. I still haven't wrapped my head around that one.
As mentioned over there, X is Froyo (2.2) Fascinate is Eclair (2.1) - a vocal few claim this isn't a big deal - I'm one of the vocal many who says it definitely is - things run faster and smoother with it.
Samsung phones come with an iPhone-kinda interface, and pre-loaded with multimedia stuff. Multimedia stuff you can add, and if you try any of the other fine UI-changing launchers, you won't care about that interface.