I think the only ball in my bag, today, is the Callaway Hex Chrome+.
If I have more than one brand of ball in my bag it's because the extras are balls that I have found, that I would consider playing. If I find balls that I wouldn't play, I either leave them in the cart for the workers. Or, I put them be a teemarker or next to a green for another group to claim.
In the past I've usually been loyal to a ball for a season. Two years ago it was the Hex Chrome. Last year it was the Hex Chrome +. This year it's the 3up 3F12. I love everything about it (just look at their twitter feed and you'll see ).
I went through my golf bag the other weekend and found several different brands that I have played... Dunlop DDH. TopFlite X'Outs. Those two brands were what I had the most of. There were a couple of Titleists, some Callaways, a Pinnacle or three as well. Those I had found on various courses in the woods, water hazard edges, or as I skirted past the driving range at the end of the outing.
I also have several Slazengers... Raw distance is what the box says. I'm not even sure Slazenger makes golf balls any longer. Actually, I'm not certain that a lot of the brands I have are still made...
But, I'm not loyal and I'll buy and play whatever's cheapest in the store or on sale or closeout.
I am loyal to whatever I am playing well with at the moment. They year before last, I played some great golf with the Penta TP5's. Last year, I shot some great rounds with the ProV1 and rode with it most if the way, or the Bridgestone B330S, which I was B-Fit for in Orlando and pre-Vegas. I'm more loyal in my bag, than I am to a ball.
I pretty much stay with the B300's or Bridgestone in general. I'm not afraid to hit another brand but since Bridgestone has been a big sponsor of THP, I tend to stay with them plus I like the balls anyway.