i guess it depends on your style. if you like to do a lot of bending, go for 8's or 9's. If not then use any string you want. The lighter the gauge the brighter, while the thicker the gauge, the more fatter and warmer tone. I have two guitars- a fender equipped with d addario 12's and my epi hollowbody with ernie ball slinkys 8's. I use the fender for rhythm work, fingerpicking, power chords etc. while I use my epi for solo and lead guitar playing.