There's a catch, though: both services have free storage caps well beneath Xdrive's generous 5GB. In the case of Dropio, that cap is 100MB. To supplement this, the service is offering Xdrive users a special premium drop, which bumps up the cap to 1GB. Normally these premium chunks of storage cost $10 a pop, and only keep for a year's time (read: subscription service).
Likewise, Box.net's free cutoff cap is 1GB. If a user wants more space than that they'll need to upgrade to a higher plan, which starts at $7.95 per month to get that same 5GB users had back on Xdrive.
So to summarize, if you're an Xdrive user looking to jettison your data to someplace besides a hard drive, either of these services is really great, but they'll cost you. The 5GB equivalent will be $40 in Dropio (for your first year, then $50 after that), and $95.40 for a year in Box.net. If you're willing to stick to 1GB, Box.net is the better deal, since you won't have to pay $10 when free premium credit from Dropio expires. You could also just throw caution to the wind, and go all-out with Adrive.from