I think the iPhone 5c will be very successful; however, I am surprised to see how many people actually stayed up to preorder one. Granted, we are on macrumors.com, so posters tend to be more loyal and excited than the average consumer (hey, me included). But the reason I am surprised is this phone is not one its buyer stays up late to preorder. The iPhone 5c is not about the tech specs; it's about the approachability and fun of color. The iPhone 5s now comes across as high end or business, while the 5c is cheaper in price and casual. People with a 3G, 4, or 4s want to upgrade, and the 5c is attractive to them. People who still have feature phones and want to enter the smartphone world now have a "new" iPhone for $99. Apple has expanded its options and will reach more people. So, I expect the majority of preorders to happen during the day. I also expect a high amount of impulse buys in person. Finally, I think Santa will bring the iPhone 5c to many homes this year in place of iPods.
It's all speculation! Apple probably won't release individual sales for 5c vs 5s, but I am sure we can get a good idea from retail outlets, carriers, etc!
(And by the way, I can't wait to get my 5s)