I'm quite easy to please really...
I have in the past always looked for the straightest grains I can find, and no more than 8 or 9 grains. I've never gone for more than that as I tend to go at the ball quite hard, and make a lot more use of my inside edge than I probably should, and therefore I've always wanted a bat that will last. In my head I've always thought of more grains equalling a shorter life expectency (possibly better to burn out than fade away though??) but increased short term performance. Having said that I probably wanted a bat to last in the past as I couldn't afford to keep replacing them which is not so much of a concern now.
Guess to cut a long story short, it's so personal, no right answer, however I wonder if there are certains things that really make a bat stand out or things to avoid at all costs.
To be honest I've always avoided any stains in the past