Ammoguide has added ANOTHER cool comparison tool and it doesn't cost anything. I've seen these links around the net:
Compare the .460 S&W magnum
http://ammoguide.com/?tool=bcompare&it=30|...|143|221|389|92
Compare the .50 BMG
http://ammoguide.com/?tool=bcompare&it=132...|99|86|76|29|28
Found the last one at the Fifty Caliber Institute website http://fiftycal.org/
You can even select which rounds to compare. (Start by removing the rounds that are there cause the compare maxes out at 8 rounds and you can't add any. Once you remove 1, you can add another 1)