That's kind of like asking the question,"which is better, Ford or Chevy?" It all depends on who you talk to.
My personal preference is Autopage. You can buy them all day on Ebay for cheap, the instructions are pretty clear and the remotes are pretty small. Their new line of the 2-way LCD remotes are the smallest in the world. I've installed about 50 or so Autopage alarms and I've never had a problem with them.
I have a Rattler by DEI. I've already sent it back in for warranty repair, but they stand behind their products pretty well.
Last year circuit city had them on sale for $50. Installation was a pain on a honda, but much easier on the kia. If you get the chance for free installation, do it. I enjoyed learning the wiring, but it took way too long.