As far as client features go I posted a detailed post in this thread over on the PEQ forums (8th post down)
http://www.peqtgc.com/phpBB2/viewtop...=12039&start=0
Trev was then kind enough to modify it and add some stuff I missed (Which i went back and added to the posts anyway hehe) and put it into a wiki page here
http://www.eqemulator.net/wiki/wikka...ClientFeatures
There's more benefits than just those lists, the things listed above are just benefits you can immediately see as a player. As a server dev there's even more you can add to that list (not being capped at 9999 max spell id for example)
If you have any questions about newer clients and their features hit one of those two pages. You can also PM me if you want I'll help if i can.
-Danyelle/Miku