I hate having things on my HD and would much rather them be web/cloud-based. I use the chrome extension Kami and Diigo. It backs up to Google Drive. It also hasn't had any problem opening up big pdfs. I haven't tried anything like robbins or harrison's, but so far I've had no problems.
I really like diigo because it lets me mark-up web-pages. So I can mark-up a webpage like a pdf and it automatically saves the page and my annotation like a bookmarking site - it's like pocket with annotations. Scrible also has similar features.