I have a Trackman 2000 and an Aristo track cleaning car as well. I won the trackman as a door prize a few years ago and I love it. (Ok my wife won it, she never lets me forget that) But to answer your question, if I was going to buy just one, the Aristo works just fine.
I have one and it works ok. I use it to clean dirt and debris from my stainless steel. If it was pure brass track, I don't think it would do as good a job. For a brass railroad, I think the LGB track cleaning engine is the best way to go, even if it is a little pricey.
I have one--I ran it with the original pad for a while, then switched the pad surface following George Schreyer's tips I hot-glued a piece of drywall screen to the pad. Works well--you can see where it's passed over dirty track. I like the caboose-like appearance also. I assume there may be better ones out there, but this works well for the price
I converted a 2-axle aristo bobber to a track car - basically copied A Kramer's method, but used drywall screen. Part of the trick is getting the right amount of weight on the pad. The pad face is 1/8 Finnish birch ply, with a hollowed out block of wood above, in which big washers are bolted for weight. It floats on the track, and after about 3 passes, glitchiness disappears. I made a REAL NICE aluminum support plate for the drywall pad, until I realized I was going to run it on powered track.... oh, well. Hence the plywood.
However, the best method remains the drywall sander pad on a pole - A bit more work running around the track with it, but also does a much better job. If I'm lazy, I'll run the car, if I CAN'T run the car, out comes the sander/pole.../DesktopModules/NTForums/themes/mls/emoticons/blush.gif