External HD is the way to go.

What if your computer 'breaks'? You can't get to the storage site til afterwards.

As with any company, I would want to know how long it had been in business and its reputation. One thing you can try is searching for user reviews, eg, "user reviews Adrive.com" or reverse the words.

With an external HD you can also take it to where a tech might be working on your computer and s/he can transfer the material straight to the new HD

Good luck!