So, I guess time wise I would be called a newbie, but I did a bunch of research and also bought at least one bad option for my slash 4x4. A bunch of people recommend the hobbywing WP sc8, ok, it appears to work alrigt, but I read a tone of issues with it that to me just made it not worth the money (even though it was substantially cheaper than a Mamba). I ended up getting a Mamba Monster 2 (water proof) with the 2650kv motor for my slash 4x4.
This thing is AWESOME! Now, understand that I spent a decent chink of change upgrading things as I broke them with the velineon set up. RPM pieces for most of the plastic stuff that broke (A-arms, bumpers, mounting posts[pro line],bearing holders) and most of all I added MIP X-duty axles, a must have for the power you will get. So its not just the cost of the ESC / Motor you will be footing.
That said, its a lot of fun!
I run it hard on a 3s lipo and it gets warm, not hot, and with all the upgrades I made, it pretty much doesn't have any issues now, even when I go full bore into a tree (I mean when my kid goes full bore into a tree...). Anyways, that's my 2 cents, take it or leave it, but remember its your money and do what you think will be the best for you.