slash 4X4 IMO out of the 2
the summit is basically a merv with bigger tires. The merv from my experience is a wheelie machine that is a PITA to control, probably the RC I've had the least fun with that I've owned to date, and most regret buying.

Bonus with the slash if you end up not liking it for what ever reason(like not enough clearance) around $30-$35 (not counting a body or tires) you can convert it to a stampede 4X4 (what I did)