you'll get a few answers to this one. The best answer is probablty to go with the highest gauge you feel comfortable with.

I use 9's on my 24 fret guitars, and 10's on the 22's. You get better tone from higher gauges, but they are harder to bend, and play in general. For lead, I always use 9's...

YJM uses 8's, SRV 13's.... The ultralites you're using may well be 9's... and if they work for you, there's nothing wrong with them...