personally.. I would run wichever you feel is the best deal.. or has the most parts support... Both being good buggies. (sportwerks taking a few design flaws from a few different buggies..).. I have seen it beat the kyo's and Mugens..
As for the losi.. its original.. Parts are great and I think you would probly have alot more set up.. Tuning help.. both locally and on line as well..And it is right there with anything else.. the RTR scimps on a few pieces but comes well equipped..
Both motors SW and the losi Mach.. run well.. the losi may have a slight edge here.. May even be too much depending on your sons ability..
the Raven Im assuming was electric..??.. even considered a 1/10 gas truck ae gt2.. or the likes..
I guess my biggest concern.. and Im sure you have thought of this.. is a 8lb buggy moving at 45 mph.. could be a pretty dangerous weapon if your son wasnt careful...Im not assaulting you.. or him.. He may very well be able to handle it!!... : )..
All things considered if you yourself dont race nitro or arent used to it,, it will be a whole new level of things to learn.. sometimes motors get the best of you no matter what precautions... ( tuning wise..)..
I do wish you luck with whatever you decide...