To each their own but if you want to get technical, your slipperential is a transmission. The only difference is that yours is exposed and uses a 1/8 diff.
Personally I'd rather drop $30 for the Traxas diff and call it a day. Don't get me wrong, I'm all about improving my vehicles but I've found that I really need to pick my battles as I got to the point where I was spending more time building car parts than I was actually driving them. I'm getting to the point where I'm starting to turn things around
