If you buy a top spec car then you cant go wrong, of course some kits have minor faults in design and manufacture etc. But those are only small bugs which are usualy ironed out in the cars first year of competition.
I think as far as top races go, the range of cars and drivers that are winning these days I honestly couldnt pick out a car which is dominant or wins more than others. About a year ago I would have said the TC3 seems to win the most but now anything and everything has won and is winning