We use these all the time, more for hunting than ice fishing, but they're handy to have any time. I went with new Motos last year, "10-mile", and they're great. The most important things are:
1. A key lock so you don't hit the buttons by accident, and a tone/roger setting so you can turn off the annoying confirmation beeps.
2. Easy multi-channel function. You want to be able to use subchannels to avoid overlap with other FRS/GMRS users. The Motos generally come with 11 main channels and each one of those has a large number of "squawk" subchannels. If you get one of the higher-end models it may include more main channels up to 22, with channel 20 being the National Emergency Alert channel. But those are usually more expensive. If you don't mind paying a little extra you can get one with a weather band radio built in, which is nice if you're going to be doing any multi-day trips with the radios.
3. Maximum range you can find. The newest ones still use just 1/2 watt transmitting power, but are rated at 15 miles or more (under ideal conditions).
4. A lanyard loop is a bigger help than you'd think. Hanging the radio around your neck is a lot easier than fishing it out of your pocket with your gloves on.
5. Rechargeable battery packs are a must, but try to get the kind where you can also use 3 AAAs in a pinch. if you do multi-day trips, you'll want to be able to bring extra commodity batteries without worrying about buying extra proprietary battery packs ahead of time.
6. Finally, it can be helpful to get one with fewer buttons on the front, opting instead for a better LCD screen interface. The more buttons, the harder it will be to use in the field when you're half frozen and don't want to take your gloves off.
That's what I've found, after researching and experimenting in the field for a while.
