String gauges are very personal but I've found that higher tension strings, especially the low 3, work much better for crunchy/pounding rhythm work particularly when you do a lot of down picked muting. They simply respond faster with less flop. I know that some guys can make light strings work for metal rhythm but I can't. Considering that a thick pick and heavy pick hand attack is part of that sound heavy strings are just needed. Maybe Mr. Sneap can give us some input on this but to my knowlege every monster rhythm player that I can think of uses heavy strings.
So ... I use 25 1/4" scale guitars and I use a custom string set so for standard tuning from low to high: .052, .044, .036, .017, .011, .009. This in conjunction with a fairly high action on the low end and medium action on the high end. I have a very heavy pick attack so this is the way that I have to set up my guitars. For drop C# I use: .060, .050, .042, .020, .014, .011.
I've tried to use lighter strings with the goal of learning to have a lighter pick hand but the rhythm sound always suffers. (Sigh!)
