In reply to Godwin:
I always thing grip strength is a measure of how hard you can squeeze something, whereas finger strength is holding your fingers in a fixed position (such as half crimp) with more weight, or off a smaller hold etc...
Some holds are all about grip, such as a flat pinch, or a tufa others are all about finger strength, such as a small crimp on limestone...
But of course some are a bit of both, like when a pinch or large grip hold also has a bit of a lip on it that allows you to crimp it too.
This is probably all bollocks, but that's the way I think of it anyway.