Here's an interesting reference guide that I found. Note that I nothing to do with comprising the information, nor anything to do with the shop that did the legwork. I will say, I've ordered from them and they are top notch however.
Here's the blog entry:
Rio, Airflo, SA Fly Lines: Review & Product Guide | The Caddis Fly: Oregon Fly Fishing Blog
And the chart:
I've used it for reference, but just like sweetandsalt mentioned, comparative analysis is always best--though not cheap.