Hiya mate, i am in the lucky position to have both of these cars, and as has been stated, they are both very different beasties, depends on what you want really, probably for out and out fun just bashin, the baja is hard to beat, been out a long time, hop-ups are endless as are different engines, really the skys the limit, 2wd hard to control on a track, bashin huge larf. The Losi 5t, brilliant piece of kit, it handles superbly, seems tough, and will most likely be the biggest seller in 1/5 scale this year, expect to see hop-ups galore in the next few months, as the yanks have gone bonkers on them, for good reason.
The Baja can be awkward to work on, due to the chassis configuration, everythings crammed in fairly tight, but once sorted it is pretty much run it till it breaks, the Losi, being the more track orientated will probably need more care and maintenance, but is so easy to work on, really is a doddle.
Bottom line, whatever one you chose, you will have brilliant fun with, i have in both of mine, hope this has helped, good luck mate.