I might be alone here, but I actually really prefer Box to Dropbox even though I do not use the desktop sync tool very often (though I've tried it). I'm sure the free 50GB I've gotten skews my opinion. For a college student like me on the kind of budget I have, knowing 50GB from Box will never go away versus getting maybe 10GB for free only temporarily at Dropbox makes a big difference. It's useful to have that kind of space for school, work, or just family sharing.
FWIW, I've never really had any issues with it being bogged down even when using the desktop sync tool. So your mileage probably will vary.
I'm upto 18.9gb permanently free on my Dropbox account. They periodically do promotions that give you permanent space. After using Dropbox for 5-6 years I'm still only using 62% of that space. For just storing documents, code and the odd file I'm sharing with people I've had no issue with the space available.
Last year there was the 'great space race' where they were promoting to students, I think I got 8gb for that. (https://www.dropbox.com/help/390/en)
Before that there was a beta for testing out their new photo system. Which gave a max of 5gb free. (It appears this is still available to give you upto 3gb https://www.dropbox.com/help/287/en)
FWIW, I've never really had any issues with it being bogged down even when using the desktop sync tool. So your mileage probably will vary.