Pieps is basically setting the standard these days. The DSP Tour is a less expensive option than the DSP and is basically the same thing. One difference though and this may make a difference for some. If you are like me and enjoy riding with your pooch. Pieps makes a transmit only beacon for your dog. Cody has been using it for a year now. It transmits on a different frequency than the 457 standard. The DSP can switch over to receive that beacon. That way you are not digging up your dog before your friends. All it takes is a DSP running the current software. If you don't have it, updates are quick and easy to get at a Pieps retailer. Receive range is the best in the biz for digital receivers with Pieps.
The Mammut Pulse is another very nice beacon. I've played a lot with the Ortovox 3+ and think it's also fairly nice.
The Tracker 2 is solid if bare bones.
All said, buy a three antenna digital beacon. If it's two antenna like the old tracker, move along.
The best beacon of course is the one you know how to use. That means practice...