Personally, I have found the following attributes to be the most useful:
|Keeper:||DEX / AGI / ALE|
|Chaser:||ACC / DEX / SPD|
|Beater:||STR / ACC / STA|
|Seeker:||SPD / AGI / STR|
In addition, BAL is useful across the board - though not as heavily weighted as any of the above.
CHA is almost certainly useless in matches, but a boost to club popularity (which can mean better finances).
MOR, while sort of useful for Seekers, is also pretty much a dump-stat across the board.