I'd like to hear from David since he has both, but also anyone else with experience with these two units, to compare them. The problem with the Decade, for me anyway, is price. They're waaaay spendy. Considering compliance issues, it would have to outperform everything else on the market for that kind of moolah.
The Decade MS-100 (mono) is, quite simply, the best Part 15 type transmitter I've used. Absolutely no hum, sounds great. Durable too, as I had one in a weatherproof box mounted just above a metal roof for several years, running 24/7, with absolutely no problems. They're a plug and play type of unit; Decade sells them trimmed for either the U.S. or Canadian markets - you set your frequency, plug it in, hook up audio, adjust the telescopic antenna length based on a chart Decade provides (to get the best performance at a given frequency), and you're cooking. I have an older one with a plastic case; the newer ones have metal cases. I have the one with RCA inputs only, but they can also come with balanced inputs.
The Panaxis ACC-100 (mono) is a good transmitter. The sound produced isn't as 'full' as the Decade, and it was difficult to eliminate hum. I had to replace the power supply, and even then there was a low-level hum in the background (admittedly you would only notice it in the dead air spaces). It has a wire antenna, so you have to fiddle around to get it to the orientation that you want, and, of course, is not adjustable in length - that means that you're sacrificing some performance. Apparently, there are some modifications you can make to increase power, but that, of course, would void certification.
The list price for the Panaxis is $199 (from their web site), the Decade from dealers is around $450. If you're experimenting, the Panaxis is a good choice. But if you to actually broadcast regularly, and can afford it, I'd go with the Decade; there are good reasons it costs more.
the ACC-100 is just an FMX (300-500mW) transmitter cut back to part 15 levels. add a bigger supply and change a couple resisters and you get 300-500mW TPO
I second the Decades. I have looked at their data on the FCC site. they look to be a very solid transmitter. kind of like an FM Version of the AM1K Rangemaster.