[derefr]

I think there are two kinds of "reliability" getting conflated here. There's reliability as in "this is built on the stable foundation of a big system and has a bunch of engineers ensuring it's Highly Available" -- both Google and Dropbox can give you that. Then there's reliability as in "this product won't blow away in the corporate-political wind" -- and Dropbox is the only one who can truly say that. (Though Google Drive is pretty core to a lot of stuff Google does, e.g. Android, so it's probably not going anywhere either.)

[UVB-76]

On the other hand, Dropbox is a one-trick pony, providing a service that is easily replicable and becoming increasingly commoditized.

Dropbox don't even own the hardware they store your files on.

Google own the data centre, the hardware, in many cases the device (Android devices, Chromebooks, Chromecast, Google TV etc.) you use to access their services, and increasingly (with Google Fiber) the connection between you and them.