I bought Crucial simply because how they have there website set up so it's easy to choose the right RAM for my system. It also ended up being a lot cheaper than my local reseller who specializes in selling OEM products.
That has a lot to do with it as well. The Crucial website tells you exactly what RAM to buy so you don't make a costly mistake. You can comb these forums and see all kinds of problems with incompatible RAM because people want to save a few bucks, but in the end, its just not worth the hassle. Buy what you know works from the get go and keep your G5 out of the hardware experimentation arena.