Standalone CRM vs Gmail based CRM?

This is a follow up to my first question "Yet another CRM. Should I build it?". For which I got good response and ideas to get started.

However, before jumping in and start building stand alone CRM. I wanted to know if Gmail based CRM like streak is better than a standalone CRM. Which one would you prefer for your next CRM solution?

I've explored many alternatives to streak and rating/reviews are good for all of them. User base is also strong. For example streak has 213,799 users as per chrome webstore.