Saturn or Jupiter
I'm with you on the more-birds-one-probe issue. I'm not sure why one would choose Ganymede over Europa unless that mission profile really does allow more Jupiter system-wide observations than the Europa-optimized mission (due to orbital dynamics or instrument choices or whatever).
But consolidating is the easy part. :)
Which one: Big Jupiter Mission, or Big Saturn Mission?
I vote Saturn at this point, though I'm trying to come up with a better reason than "I think Methane lakes and rivers and ice/ammonia volcanoes sound cool!"