If you want one that runs relatively smoothly on an Intel Integrated Graphics (like I do), go with Liftoff. If you have a better GPU, go for Uncrashed. You can customize all sorts of settings, such as drag, kv, stator size etc etc, and its graphics are better, and its maps are bigger (I think), and the racing is way better than in Liftoff.
Though, many people say that the physics in The Zone are some of the best, but it only has a few small maps.
Hope this helps!
:)