PC or console versions of these games if my PC isn't that powerful?

So I have a PC that is not too powerful by today's gaming standards and is a compact unit that is too complex for me to bother upgrading at this point. It can run some new games good enough for me like Left 4 Dead on medium setting, enough that it was worth getting the PC version even though the console version runs smoother. Some other games like COD4 and Bioshock are playable but are choppy enough and require turning graphics down enough that I would go for the console version. So I am wondering if some other games that are better on the PC would be stable enough to warrant buying them on the PC rather than the console version. Specifically I would like to know about: Dragon Age, Mass Effect, Fallout 3 and Borderlands. Thanks