I agree. Yes a pimped out 3.1 is not to different to 3.9 generally. But the 3.1 will be patched to buggery, and in my experience will fall over a lot.
I use 3.9 on my 030/50 A1200. It runs well, but you will still have to run a few patches to get the best performance out of it Fblit, Ftext etc).