I think the 5050 is the more popular camera now, since it has an excellent array of features and takes 5 megapixel photos. Basically an excellent all-around package.
As for myself, I use and love the C-750. If you look at my gallery on this board, all the photos you see were taken with the C-750 in a PT-018 housing (although now that I think about that statement, I can only hope that viewing them doesn't sour you on your choice
). When I was in the market for a digital camera, I took a long hard look at the 5050 before going with the C-750. For me, the C-750's 10x optical zoom was the deal-maker, since I wanted a camera with the highest optical zoom possible. I was willing to sacrifice a megapixel of resolution in order to get it, so the choice for me was obvious. It's an excellent choice for above and below the surface, and I've so far had no reason to regret it.
But take heart. We C-750 owners are a small, quiet minority, but we lurk around here anyway, feeding mostly off the table scraps from the 5050 crowd. If you have any specific questions, post them and I'll try to give you some useful answers.