The 6505 (haven't tried it, got the 5150 but it's the same as far as I know) is an awesome amp with great power and distorted tones, but when it comes to versatility, it can't beat the Powerball. The Powerball's also got lots of raw power, great distorted tones AND superb clean ones as well which I can't say the 6505/5150 have. As far as my own experience, the 6505/5150 for some reason does cut through a little bit better live, but that can have other reasons too. At low volume, the Powerball does sound better, the 6505/5150 needs to be cranked quite a bit to really come alive.
But for recording in a bedroom in an appartment, I believe they're both too loud.