Dwarves are no longer stuck with being a gunline army, thanks to the random charge range. Especially if you take a look at the pics in the BRB (or perhaps Very Big Rule Book ).I agree with the above posters. Choose the army you most like the look of.
That aside, it also depends on what type of army you want to play. A sturdy gunline (Dwarves)? An elite army of specialists (High Elves)? Or a resilient close combat army (Warriors of Chaos)?
If all you care about is competitiveness, then Warriors of Chaos are probably the most competitive, just because of how cheap marauders are.
In terms of competitiveness, I think High Elves are better than WoC, thanks to ASF+high Initiative+Great Weapon and of course Teclis. No wonder that they are in the new box and the Skaven, the other most competitive army. WoC is in the third place at best, but I think we'll have to wait a few months 'till the tournament-zerkers find out what can be found out.