Doug,
Luckily for everyone, I'm not a rater! Irondequoit and Schuylkill are very different in both terrain and how they play. Schuylkill plays up and down the side of a mountain in Pennsylvania coal country, meaning that everyone hole features one dominant slope going one direction. Irondequoit, like most courses in Upstate New York, has no dominant feature like that, but instead it features several micro-contours that create very interesting routing prospects. What differs Irondequoit from other Upstate NY courses is the dramatic, swooping nature of those contours. Think of the wild fairway contours of an English links course tossed into a parkland setting. While Schuylkill gives the player several sidehill lies in the fairway, Irondequoit gives the player all sorts of madcap stances. As Lester George points out, Irondequoit doesn't rely on fairway bunkers because the terrain is so good and so unique. To me, this is a major advantage for Irondequoit.
As different as the two courses are tee-to-green, the differences are even more profound at the greens. Irondequoit relies on smaller (shrunken, perhaps?) greens that are, for the most part, subtle, with one dominant slope or contour. At Irondequoit, the greens are a complement to the wild terrain. It's as if Ross looked at the wild land and decided that the greens would occupy the flat spots, and the fairways and greens would occupy everything else. Schuylkill, on the other hand, relies on big, bold, WILD greens, with all sorts of rolls, counter slopes, and shaved-down falloffs to challenge the golfer. Thinking about it now, Schuylkill is very similar to Mountain Ridge, both in terms of the piece of property it occupies and the way it defends par. Mountain Ridge is the better course, but Schuylkill could get there with more restoration and tree removal (c'mon Mark, when are you getting on the grounds committee?) Another similar one that comes to mind is Mark Twain, which, interestingly, was also built later in Ross's career.
All of these differences are understandable. The two properties are completely different at Schuylkill and Irondequoit, and they were built at different times. Also, Schuylkill has a Willie Park element as well. While I like Schuylkill, I'd give Irondequoit the edge. It has a lot more variety to it, and the terrain is so distinctive that it merits a special trip to see.