I use D'Addario XL's.
The gauges vary according to my guitars....but basically I love G-Strings! ;D
My string gauges depend on many things.
What type of music, tuning, guitar, neck scale, guitar configuration, and sometimes personal preference.
I play mainly rock classics, instrumentals, or blues. I have guitars with 24.75", 25.5", and 26.5" scale.
I mostly play the electrics, but also have an old acoustic and nylon string classical. (Martin strings)
I generally like to play instrumentals and use a whammy bar. Thank God for the locking nut! Once the strings are stretched, you pretty much hold tune until you toss the strings. I like having various floating bridge and fixed bridge guitars set up with strings for certain music I like to play. I don't mind changing out strings, but I try to keep enough setups, so I'm not. I change strings more often than most guitarists. I spoil myself, as I really like fresh, bright sounding strings. I get 12-20 hours of playtime on a set, and I toss them.
Main thing in my string selection is balance. I like to keep the string tension well balanced across the neck. [whole subject of it's own]
It comes out basically split gauges, like 10 bottoms with 9 tops...as an example. Some guitars do need either the 5th or the 2nd string to be a hand picked gauge. (those are typically the most unbalanced) All guitars are going to react different to the same string, because of stuff like head or tail angles. A Gibson head angle drops steeper than say an Ibanez head. The total string tension will vary between approximately 100 lbs. to 140 lbs. according to scale length, tuning, and gauge, with most important as uniform a tension as I can get with the wound string groups and the plain string groups.
[simplified... I'm looking to keep the same string tension on all 6 strings...and stay within a total of 100-120 lbs. total]
Most guitarist don't know about this...and have some strings with a big tension next to a string with lessor tension...and it will screw with you... if you are doing fast licks, string skipping, arpeggios, legatos, etc. You really want your fingers playing against the same tension, so you aren't over or under fretting. That's how a lot of players give horrible sharp or flat notes,.... they may not hear it, but everyone else does... ;D
Outside of alternate tunings which require special attention to gauge selection, my standard tuning (or) Eb tuning if a very well balanced tension, will help with harmonics, intonation, and due to uniform string action, improves picking, and note voicing.
The shorter the scale neck, the lighter the tension, so I do tend to stick with 10's on the 24.75" necks, and 9's on the 25.5" necks.
The 26.5" neck (Baritone guitar) is a whole different animal, and I'll run anything from 10's to 13's and get more involved in alternate tuning...but basically I'm lazy in that regard. It's a lot of work setting up...even though that guitar is a string through fixed bridge. The floating bridge are even more fussy and time consuming, but I've gotten good at setting them up.
Where I live, the humidity affects the neck, and I have to adjust the truss rod on all my guitars twice a year. The average humidity in the winter is 25% and in the summer 75%.
Set ups take time, but I actually like doing that. Fact is...I'm more of a luthier/stagehand than I am a guitar "talent".
I envy guys who have real talent playing guitar... but then I have natural talent with the tech stuff. Most of these guys are SOL without guys like me to make their guitar sound sweet. You can have a $20k guitar sound like crap, if it's not set up right. ;D
Another thing... I hate the stage...outside of doing the stagehand stuff. I've tried being in a band, and absolutely hate it. What I've done mostly, is appear as a "guest artist" with my favorite local bands. I would do a particular song real good, so I'd get up onstage and "rip one off."
One time, I did this, and Mitch Ryder (Detriot Wheels) was in the audience. He came up to me afterward, and bought me a drink and told me I was fantastic. (best compliment I ever got from a Pro) I didn't want to let him know how much I really suck.