Joe's is what I consider the most helpful, but you have to get used to it. Altitude has a great chart, too, and they've tried to apply Innova-type numbers to other brands. I use these two the most when comparing brands or looking for something new. Each has errors (and this will depend on your individual experiences or throwing style compared to the guys who compiled the chart), but they're both very good. Comparing a disc's ratings between the two charts will tell you pretty much where it is in real life. Either both charts will agree, or the truth will be somewhere in the middle.
I like the idea of Marshall Street's visual grouping, but it's so full of bad errors that I don't even look at it anymore...super awesome dg store for sure, though! But dang that chart needs some serious revamping.