If on a budget, a 4x4 Slash w/ upgraded shocks & center diff or PE.
If you're thinking you REALLY want a 1/8 buggy for the long term, just pay it and commit to what you really want.
If you're new to RC or relatively new, Slash2, Slash4, Slash4PE.
If you're not, then consider the 1/8. More complex and (for me at least) more maintenance/wrench time.