Love the post, I find myself having to make a similar decision. Looking to get a new SC truck myself, (i have a blitz) for racing, and have found these two on top of my short list, along with the Kyosho SC-R.
I think you may want to head down and see what other guys are running at your track or area to get a better idea. Make sure whatever you buy, that the lhs or track stocks parts for that model for when stuff breaks and you need quick repair turnaround.
You should also check your track for the different classes that are run. My local track has a rookie class, for all beginner drivers, and there is no rules for motor size, so the RS would be fine. But when you're ready to step up to sportsmen stock, they limit you to a 17.5 turn motor, so the RS motor is out. Next class up is expert where theres again, no limit to motor size. This can all very from track to track and then theres roar's rules that will apply should you start running at these events.
I think I'm leaning towards the Losi at this point. It's less cost up front and will be a little easier to learn with being less powerful than the RS. Once you get comfortable running the losi stock, then look at the path to upgrade, which is pretty sweet. Get the TLS kit, a brushless combo, better electronics, etc.
One last suggestion would be to get the Losi roller ($170) as opposed the the rtr kit. Then pickup a cheap, but very good radio (FkySky GT3b, $35) followed by a decent brushless motor/esc combo (Hobbywing EZ run, $60)
certainly no worse than the reedy system on the RS and bam...your at less cost than the RS...good luck at let us know what you decide