To second what Dave said above, in WHFB you pretty much have to LOVE the look of the models that you are going to be playing with because, unlike in 40K, you are going to be painting a TON of those same models over and over again. When you're talking a couple units of 10 guys (like in 40K), boredom usually doesn't get a chance to set in. Take it from me, though- you aren't going to enjoy slogging through a single unit of 40 guys, all painted similarly. . .and then doing that again and again for your other four units. . .in an army you don't like the looks of.
So, the best bet is to always choose the army you are stoked to paint and game with. Simple, but that's that.
As for your three choices- all have a great model range. Dwarves play mostly defensively, WoC are pure charge and assault, and High Elves are the most "strategic," in that you definitely have to pick and choose your battles and make sure that you maneuver well into place. All are fun to play- HE's are definitely the most challenging, in my opinion, both from a gaming and a modelling/painting perspective. So, that could also come into play, depending on how experienced you are with the GW systems.