narrow kerf

I use Stihl products. Right now I run a 25" bar, 3/8 .050 chains. I have a 20" bar, .050. So, to try narrower kerf, with Stihl specifically, do I go to a .325 with the .050 or do I stay with 3/8 .050 and go with a 3/8 micro, lp, or picco 3/8? Thanks for the help, it's greatly appreciated!