Between the two options, I'm partial to SDExplorer, because--for me, at least--SkyDrive's capacity is its primary attraction, and limiting the amount that I can sync renders it relatively uninteresting. Plus, Live Mesh isn't really ready for prime time on the Mac, and I've experienced weird issues getting the Mac version to share the same folder with the latest Windows version (oddly, the still works fine across both).

Overall, however, neither Windows Live Mesh nor SDExplorer really gives you as much multiplatform usability as Dropbox does. While SkyDrive is getting great integration on Windows Phone 7, it remains mostly a browser-based experience on other smartphone platforms, with serious limitations.

So, should you dump Dropbox for SkyDrive? It depends. If you live almost exclusively in Windows and don't need much mobile access to your files--or if you use Windows on the desktop and Windows Phone 7--then SkyDrive is a no-brainer. But if, like me, you're constantly moving between various platforms in the course of a day, Dropbox is still the king of cloud storage.