Here's a comparison between the original canon grip and an "opteka" grip.
While this is for the BG-E3 (for the 350D) while the grip in question is the BG-E2, I'm assuming that the results would be similar.
edit: forgot to include the link!!!! here:
http://www.michaelduvall.com/bge3/
Sending your gear to Gary is another option!
Sorry, I've only got the original grip, so I can't comment on the 3rd party grip. Even though the third party grip is available, I' still go for the original - just for brand preference