I use the Crower stainless steel Enduro rockers on my engine. They are very similar to the pro magnums. Stainless rockers don't add that much weight and are a lot stronger. They usually cost more though. Aluminum rockers are lighter though which is a slight performance advantage but won't take as much abuse.
The Crower Enduro aluminum rockers are the ones that look like the Scorpions.
I like the stainless rockers better for a street/strip car because they hold-up longer. For an all-out strip car you can get a couple more ponies from aluminum rockers (not sure how much though). Stainless rockers are usually better for circle track cars since they are more rugged for the longer race periods although I know a lot of guys that use aluminum in circle track racing too.