I think MechQuest is more for people who are more into robots and androids and what not. DragonFable on the other hand is for mages and knights and stuff, and I'm more like that so, I think I'll go for DragonFable!
Well, I have played both, And as Nichodemus has said about Mechquest, I found that problem too. And dragonfable I did actually play for some time. Untill I relised that it was pretty bad.