I'd concur with Nachtmahr, which of course should be the default position in any event. I've had some lopsided players on the JS/JR curve in both directions, including a 9JS/19JR guy, and both extremes seem to be fairly unimpressive from beyond the arc. I've also got some guys who have more JR than JS but not an excessive amount (15/18, 14/18, 14/17) and they tend to shoot pretty well from beyond the arc against decent but not toplevel competition, to the point where my team is better from three than from two, though the shot distribution of course doesn't change because #reasons.
Based on what I've had in the past, I kind of like the JR a couple of points higher than JS, but realistically the only answer to "do I need more JR or more JS to hit more threes?" is "Yes."