The technology put into the TC3, is a newer concept, than that of the Pro2. HPI is already out with the RO4 (Pro4) now....which improved greatly upon the Pro3, and which the Pro3, did the same with the Pro2.
Parts are going to be growing scarce with the Pro2 shortly (if not already), because the factory makes only so many extra, and molds get destroyed, and then you reply on aftermarket companies to keep the parts in stock, which all goes with supply and demand....see where I'm headed here
At any rate, this from experience, owning a Factory Team TC3 and a Pro3 at the moment, I would have to say I like my TC3 because it is shaft driven, and I just love that....very maintenance free, and shafts rarely, if ever....break!
Now, I did not see anywhere mentioned, what series TC3 you have, whether it be Racer, Team, or Factory Team? This makes a difference in the abilities of the car, and the setup. Either way though, I would concentrate my funds probably on the better car, IMO, the TC3, whichever series it may be. Latest technology put into a touring car by AE, many many parts and hopups available, and is very competitive on the track!
Good luck!