What you you rather have? I'm an AMD noob so I dont know whats better, I do know that 939 is ultra popular but arent they going to stop making new CPU's for it?
Am2. Its newest and there are no major flaws. Anything new is buggy. I dont think anything major though.
Besides, it uses DDR2 memory, and its the newest, so upgradeability in the future is much more likely (actually inevitable) then 939 that will slowly die. Although it will be around for a few more years.