Just wanna say that the Wavebird is a very good controller, and the batteries last for weeks of solid continued play. Don't have much experience with third party controllers for Nintendo as I like to go for the best, but when it came to getting a decently priced wireless controller for PS2 it turned out to be a third party one...it works very good and the batteries actually last quite awhile.
It may end up being hit or miss in this situation, but you can always save your receipt and return the third party one if it turns out to be a piece of junk and get a better one...the price difference is certainly substantial.