TC5 is a belt car, so naturally it will be easier to drive (I know this first hand) The TC4 being shaft driven will have a bit of pull one way due to the nature of a shaft car. The TC5 seems very consistent no matter where I take it and I would HIGHLY suggest it. As for building and maintainance... the TC5 was the first "racing spec" touring car that I ever built and it practically put its self together. And aside from the usual maintainance (cleaning, nut and bolt check, ect..)the TC5 is no tougher to maintain than any other car I have owned.
As for the brushless question. Everyone seems to be switching from the GTB's to the LRP Spheres. And using Novak 13.5 motors. From what I understand, the Sphere just has more punch. But im sure there are plenty more people that are more knowledgeable that I am who can tell you better than I can.
At my local tracks we run brushed with brushless and lipo with ni-mah... this will vary from track to track, so await the response from the race director. I am looking to switch to lipo due to the sheer ease of use. When you take discharging out of the equation, it frees you up to work on the car and not have to worry about it. Also, the lipo packs will not loose punch like a ni-mah pack will.
hope this helps!
-Keith