From what I've seen, the DR10 is probably the "best" platform to start with. You can basically drop in a DRK with a 3.5t and run 2.1s all day.
The drag slash is loose, difficult to make go straight, but the velineon motor packs a punch. It can run on 3s vs most 2s outlaw builds and is actually a better car on 2s if running box stock.
The Losi is probably the most tuneable and comes with a serious 2s motor out of the box, but it seems to be the touchiest of the lot. It should be able to run faster than the others on 2s out of the box, but it takes more tuning and driver knowledge.