The 260 and 270 really don't have the nards to pull the more aggressive chain especially with longer bars. Modern saws depend on speed to get the job done, you want 3/8 chain go with the MS390 or better yet the MS362.

CG is right within the Grunt within 50 cc Class Saws for the larger Gauge Chains , especially in Hard Wood (Maple , Oak) cutting. If you wish anti-dirt intrusion
and abrasive resistance in Soft (Pulp) cutting .325 wins out but at a price. As far as Model 260-Pro would be my recommendation over the 270 . As far as the 390 , I would again favour the MS-362 or even better the former MS-361 which is still available within numerous Dealers.

Thanks for the advice. That's a big help.

You'ld want to run .325 on a 260 or 270 Steve