I like having a clear pecking order in my lineup. Unless you truly believe that a bench player's level of ability has risen over your starter (which usually takes a bit of the season to figure out), stick with that pecking order. That way, even if I leave stats on the bench, I don't beat myself up over it.
I know sometimes you can't always get your roster to work out like that. You can use batter vs pitcher info (but don't read too much into limited sample sizes), home/road and platoon splits. Sometimes I'll just leave the guy with the latest game start time on the bench, so I have the flexibility to sub him in if another starter unexpectedly gets the game off (or the game gets called due to bad weather)