Google Drive is the best. More flexible plans (Dropbox and Drive both offer 1 TB for $10/month, but Drive also offers 100 GB for $2/month, 10 TB for $100/month, etc.) The web interface is the slickest web app I've ever used, and it has the requisite desktop uploader and smartphone apps. Sharing controls are world-class. You get version history for every file for a month back.
If you can, do both Google Drive and Dropbox. Redundancy is its own reward, and they're easily both head and shoulders above the other competitors (especially now that Microsoft has basically surrendered the fight.) But if you only had to choose one, I'd go with Google (WHAT A SHOCK.)