I have the same problem, as I have a personal and a work Google account. Chrome can sometimes ask you if you want to switch accounts, but in the end, I use Firefox for personal stuff and Chrome for my work.

BrowserChooser http://browserchooser.codeplex.com/ is a nice tool (like Choosyosx) to help select what URL to open in which browser.

To sync to Google Drive, I use Syncdocs http://syncdocs.com which is an enhanced Google Drive sync app that enables syncing multiple accounts at the same time.

I think Google wants each user to only have one account, which makes it better for them tracking ads.