RE: Nitro or Electric??! Help
The Savage XL comes with the three speed and a honkin' massive big block, so it should, if only just, be able to make about 40MPH. It will be nigh uncontrollable at those speeds though, given the top-heavy COG monster trucks come with. Protip: Do NOT steer at those speeds if you don't like barrel rolls. Acceleration will also leave a bit to be desired, it weighs quite a bit and it's designed to stand up on it's arse instead of move forward quickly, so you'll have to be judicious with the throttle application through first and possibly second gear. I've seen them ride wheelies all the way through third but I don't think there's enough torque once you've shifted out of first to pull one.
Plus side? Nothing sweeter than hearing two shifts in a speed run!
As for a buggy...depends. A 1/8 buggy will be a bit worse off road than a monster truck, but that's mostly due to it's center diff. Try crawling and you'll just spin the inside front wheel. However, they have ample ground clearance and traction, so as long as you keep the momentum up they'll handle off-roading just fine. They'll also hit 40MPH without any trouble at all, they don't even need multi-gear transmissions to do it, and they will handle worlds better than an MT.
The Revo? Steer clear. That thing doesn't know what it wants to be. Part of it says "LOOK AT ME, I'M A GROUND POUNDING BAD-ASS MONSTER TRUCK! RAWR SMASH CARS BIG AIR!", while part of it is saying "Psh, I'll run hot laps all day long. Throw me on the track already." It's a jack of all trades, master of none issue. It's a bit too heavy and underpowered to be a good race truggy, after all it's only packing an over-bored smallblock, yet it's too low slung to be a proper monster truck. It's only a decent buy if you can only afford one vehicle and want to have something that isn't completely incompetent on the track, but don't expect it to run rings around RC8Ts.