i used serebii when i was playing diamond.
Serebii, since its pretty much the only reliable and extensive one out there...
( All Gen. Pokedex's, Attackdex, ect. )
Serebii pretty much 99% of the time.
Sometimes when I'm lazy and I'm just looking for a Pokémon's number or something, I just go to
http://www.pokemon.com XD
SPP -_-...anybody who says Serebii is referring to Joe...and yeah, SPP's easily-accessible and user-friendly dex wins completely. No bells and whistles needed...
Serebii's by far. All the extras they add help out allot. They just added the move combo finder, and that's help me so much already.
Serebii's for me too, no fancy useless stuff but a lot of helpful stuff. Some of the new things he's added to it in the last few months just make it so easy to find anything.
I've always used Serebii's. It's simple to use and it has everything needed.
You know, I'm running a topic like this at another well-known Pokemon forum, and there, Veekun is way out in front, in case you didn't know. However, here, it looks like Serebii is the dominant 'Dex.
AND SPP! lol, it's really good and all that that's posted already.