Disclaimer: I've been using an electronic logbook of my own making since the ancient DOS days and, at least for now, continue to maintain my paper log, so I am a little less concerned about loss of data by using an online logbook than I might otherwise be.

But, I recently began using myflightbook.com. It's been around for a couple of years; in fact it turned out I had an account with them since 2008 when I was looking around.

The data is kept on his servers, in the cloud. What finally brought me over is that, including being accessible online, the developer has both an Android and iOS app that he continually improves.

Added to that, from a data security standpoint, he also has an Excel spreadsheet you can download and which you can update the data in it from the cloud.

The developer is also very responsive to comments and seems really interested in improvements.

Depending on what your needs are and the usual issues (data security; what the FAA things an eLog "acceptable to the Administrator" is), I think it's worth a look. Obviously, since the data is the cloud, there's no syncing issue. Wherever and however you acces it, it's the same data.