Don't take my opinion for granted- I'm only in my first full season, but from my point of view...
I have 4 SG's/ PG's
One has 5 JS and 7 JR, 8 Handling
One has 7 JS and 7 JR, 7 Handling
One has 8 JS and 7 JR, 7 Handling
One has 4 JS and 8 JR, 4 Handling
The 4/8 one is far lower shooting percentage than my other players, but is still very good at shooting- the one that performs best is actually the 5/7 one on most occassions, with the 7/7 one and 8/7 ones giving me 40 points in a game once each- the 7/7 one being the top scorer during any game since I owned the team.
I think JR is valuable if you have good JS to back it up, at least equal to the JR of your player, but I think having good Handling helps just a WEEE bit as far as shooting 3's, don't know how, but it seems that the better grip your player gets on the ball the better shot?