I recommend only one brand: the PLBs made by ACR Electronics. These are the most reliable PLBs available today and have been extensively field-tested in maritime, desert, and mountain environments. These transmit on 406 MHz, and with some models you can download your GPS coordinates into the PLB.
You can also operate these one-handed, and they are constructed to be impact- and water-resistant, unlike other PLBs out there. ACR just released a smaller version, which runs around $350.
There are less-expensive brands available, but I have not found them to be nearly as reliable as the equipment put out by ACR. I've tried out some of the other brands under a variety of field conditions and experienced only a 50% success rate. If you are going to pay for gear, make sure it has quality construction and is totally reliable. Survival gear is life insurance, so make sure you can indeed stake your life on it!
Do I carry one with me on a day hike in the forest with my dogs? No. But on a long canoe trip or remote trip in the Grand Canyon, I wouldn't be without one.