I'm a dealer and mountain rider, I run the BCA DTS Tracker II. They have been around quite some time and are easy to use. There are several models out there that are more money but may not be worth it.
You can see the DTS and find info at our web site:
All modern beacons transmit and recieve on a frequency of 457. Some have the capability of also transmitting on 121.5 which is the emergency frequency for aircraft. None, to my knowledge, will receive on 121.5. Any current transceiver will be compatable with any other brand. I think most brands available are certainly adequate, but if I am in a slide, I hope someone in the group is carrying a Tracker DTS. They are easy to use in comparison with some of the others. I would advise that no matter what brand you get, practice with it. If you ever actually need to use it, adrenaline will override your fine motorskills and make it very difficult to operate your beacon if you are not intimately familiar with it and extremely practiced. I commend you on your efforts to learn more and carry the proper equipment. Hope you never need it. And yes, I have the Tracker DTS for sale if you decide to go that route, PM me.
Have a look at the 3 antenna Pulse Berryvox or Pieps DSP. I saw a demo at a beacon seminar last night and I'm sold. Quickest way to find your buddy. But as with all beacons, practice makes perfect. Check out www.beaconreviews.com.