For regular lawn trimming I like to use .095. They sell line by the pound so you get more feet of line per spool and you can fit more on the trimmer spool so if it wears slightly faster you still have more line anyways to make up for it. Plus the thinner line causes less damage to whatever your trimming ie. fences, cable wire, siding etc. and while I may be a good enough trimmer not to damage these things the more guys I have the better it is to give them line that they cant do as much damage with. Just my 2 cents.
1991 GMC 1500
2002 Ford F-350 dump 7.3 Diesel
2004 Ford F-250 6.0 Diesel
2005 Ford F-450 dump 6.0 Diesel
2008 20' x 8.5' Enclosed Trailer
2 -7x16" Trailers
1999-2010 Exmarks, Kubota, Husqvarna and Walker mowers.
Stihl blowers, trimmers, edgers, etc.