Here is my .02 cents- Buy the Losi, sell the Rustler and then buy the esc and brushless motor off of
www.hobbyking.com for under $100. Once you start racing you are not going to be happy with a brushed motor + a brushless motor lasts longer and requires next to no maintenance.
It sounds like money is an issue and that's why I say buy the Losi. If you buy the SC10 you aren't going to be happy with it after a short time and you'll want to upgrade it. Thats what happened to me and I'm sure a ton of other people on this forum.
The hobbywing systems from hobbyking are pretty good especially for getting started and they are cheap. You don't need to go with a $300 dollar system for your first truck. Also get your lipos from
www.hobbypartz.com they are cheap and work well Gens Aces are great