Performance/best practices question - When to use Contexts and when to use regular blocks

Hello,

I just started diving into this module after WAY too long (I've always been a panels guy, which is a fantastic module as well but with somewhat different use cases), and it's totally awesome. A big thanks to all the maintainers and contributers for this module!

I'm just wondering when I should use blocks and when I should use contexts. I remember at Drupalcon a couple years ago, there was talk of blocks being kind of crummy resources-wise so I was considering only using context blocks rather than blocks, but I haven't delved too deep into the code or got my dev performance checking environment totally ironed out yet so if it really doesn't make a difference, I can see using blocks for areas where they can be used and contexts for anything that actually requires them to be better for organizational reasons. I just know how it gets when you have hundreds of views each with a whole bunch of variants and not enough time to set up tags or anything like that, you know?

tl;dr version:

Blocks vs. Contexts for things that basics blocks can handle.

Thanks in advance!
Tiuya