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Well, first off, I have to disagree with your Coke and Pepsi example, I find them significantly different. Coke is more heavily carbonated, while Pepsi is flatter and more syrupy sweet. In short, Coke=yum, Pepsi=meh.
As for Drive vs. Skydrive, you do get a little more free storage from Skydrive, 7GB vs. Drive's 5GB. Sharing documents (at least Office documents) is really easy on Skydrive, but if you are working with others on docs, images, or videos, Drive is great, making it easy for users to leave comments and collaborate. Drive has a lot more editing features, and it is quite polished. You can also save documents in various formats on Drive, including Word format, whereas you are limited on Skydrive to Microsoft formats.
If you want to use them on your mobile device, and that device happens to run Apple OS, you are limited to Skydrive. I personally prefer Drive on mobile devices because it has the ability to access files offline, something that Skydrive does not offer, as far as I know.
Both are solid choices. I prefer Drive, mainly because of the collaboration features. Drive also offers up to 1TB of storage, if you are willing to pay for it. I could easily see reaching the other conclusion, however, and preferring Skydrive, especially if you primarily use Apple mobile devices or Microsoft Office.