The biggest things here are the OCR, image recognition and (hence deeper) search feature for your files. It would be really tough for Dropbox or any other competitor to match these. The Google drive also seems to be available on all platforms so looks like a very good option.
"The Google drive also seems to be available on all platforms"
Not yet. There is no broad based Linux support yet (it supports Android, which is technically Linux, but no Linux Desktop distro is supported) and iOS support is still in the works.
