I have a 70 druid and a 70 Shammy, and while I prefer the druid, they are both very similar and also very different. Either choose the one that appeals to you or start leveling one of each. The early levels are pretty quick and you can just keep playing the one you enjoy the most (and level the other later :) )
Also, with WotLK out in the not too distant future, it would be worthwhile reading up on the new talents & abilities as some things are changing significantly. Even Blizzard doesn't seem to know how bear tanks are going to work at this stage - just that they will work!
Edited, Aug 26th 2008 11:08pm by RareBeast