In reply to wbo2:
Funnily enough we are in the process of putting together a Large Bouldering Mat Group test, which may or may not answer some of your questions. However, given that it's still a week or two away from being published I thought I'd post up a few of my own thoughts.
I personally have never, ever regretted upgrading to a larger pad. I don't think you're unreasonable for wanting more comfort either, as that is a perfectly reasonable (and sensible) request. Yes, they're heavier and bulkier, and yes there are some circumstances where two smaller pads wight work better, but if you're want that extra comfort - or are climbing at greater height - then buying a larger pad is something you'll never look back from.
Within the Group Test we'll be looking at some pads which have already been mentioned within this thread, and others than have not, including the Petzl Cirro, Moon Saturn, SNAP Grand Wham, Alpkit Project, Organic Big Pad, Ocun Incubator, Metolius Magnum and Edelrid Crux all being put through their paces.
Feel free to fire over any questions in the meanwhile, otherwise I'll do my best to get the review out ASAP.