Most folks find that the gel saddles are less comfortable than they appear, as the sit bones squish the gel out of the way, which then ends up pressing on the sensitive bits. I can't spend more than 15 minutes on a gel saddle without Mr. Happy drifting off to parts unknown. Leather saddles don't do that, though they do tend to hurt the sit bones until broken in.

I haven't found a massive difference in comfort between sprung and unsprung. It is true that it takes a bit of a bump before the springs spring. You can't expect them to really smooth out the road patter. The fatter you are, of course, the less of a bump it takes for the springs to jump in. I assume that at some weight (above 300 pounds, probably) the springs are always seeing action.