Gerard,
I suspect a poll on this subject won't tell us which one is the best, but it will tell us which one is the most popular amongst Stormtrack members. There may be a small handful of people that have tried multiple brands, but I'm willing to bet the majority of folks have only used the amplifier they originally installed in their vehicle. It may very well come down to a Chevy vs. Ford discussion. It would be great if someone had all of the different brands lined up at the same time to run tests, but obviously that would be cost prohibitive.
I went with a Cyfre "Rockies" package from Maximum Signal because it comes highly recommended from a lot of chasers, but I do not have any experience with other amplifiers, or even this one for that matter, so I cannot offer you a valid comparison or opinion. But what I can suggest is reading all that you can on the different amplifiers and then selecting the amplifier that best suits your needs. (the right bands, whether or not you desire to run dual cards for redundancy, etc.) I have an assumption that you can't go wrong with a Cyfre form Maximum Signal or a Wilson amp...so it just comes down to matching the right product to your needs and the final price. But again, that is just an assumption on my part.
Bryan