Deeper = shorter. In summer I rig in over 100 FOW for chinooks with very short leads. Under 10 feet. Early summer, not so deep -- maybe 50 FOW -- much longer leads. 20-30 feet. It's not the rigger ball I worry about -- but rigging shallow 10 feet behind the boat and motor can't be good. In real early spring when we don't bother with teh riggers, we use super long leads and inline boards to keep teh lures as far away as possible.
I've got lakers off the bottom, and a few odd rainbows with short leads down deep. But mostly salmon. Good mix of chinook and coho. I don't know if it matters much. If I had to give a hunch -- I would say longer leads for coho, shorter for chinook. Now that I'm thinking about it, I'm going to make some notes next season and see...
I run worm harnesses up to 200 feet behind the balls in Erie for walleye in 50-60 FOW. When gobies pop the riggers after setting THAT up, I get a bit furious...