This really depends how you're using it.

For driving, I had a TomTom and that got lost, then bought a Garmin. I made sure I could get free lifetime map updates. Whoopie, this means that I have to take it in from the car and deal with figuring out my online account from 1-2 years ago when I set it up. OK 4-5 years actually! I also have an Android with Google Maps. That works way better because it gets updated online and also it shows traffic. My cheap GPS only devices don't do that.

For instance if you're hiking, then maybe you just want an actual GPS. I'd look for hiking and camping ones though. We actually develop commercial products using GPS and the profile difference between pedestrian modes over vehicular are vastly different. On the roads, they can assume you're on a certain side of the road, and so forth. They tend to lock to the roads. Versus a walking mode GPS which tries to not drift as much on the fix. Either case, +/- 3 meters best accuracy which does get better as you move. Moving helps the receiver's filters to avoid the drifting which can occur when you stay stationary.

Meanwhile if you're talking survey grade, then the exact opposite and stationary is how they're designed to attain better fixes. I'm not sure if they also use the WAAS system, we've tried, but never could find enough stations to help the fix any better than what the L2 mode gave us.

For just getting around, directions. It's helpful, ... I used to live in a city and really I found that selecting tall or characteristic buildings near where I wanted to go and then keep driving towards them helped me the best. Obviously before GPS was an everyday thing. Having a sense what is sensible is good too. Just

I have a Nuvi 52 (Garmin), it runs Linux and of course you cannot update it from Linux. But it is most sensitive GPS I ever had, it works inside of my house! I just wish they could grow out from yesterday and add at least Android support.

Probably the most-important thing to look for in a GPS is ... the antenna. If the unit has "something sticking out of the top," it's got a good antenna that will actually work in the woods. If not, it just has a "patch" antenna which will let you down.

There really is no difference in performance between a patch antenna and a quad helix but I would agree that an external antenna is preferred over an internal.

I've used Garmin, Magellan and TomTom GPS and prefer the Garmin. However, I used a Garmin and TomTom overseas and the TomTom worked better. I brought the Garmin from the US and the TomTom came with the rental car.

I am referring to the internal vs. external antenna, and I'm also talking about devices used for hiking (and geocaching) in the deep woods of the American southeast, with their delightful but dense canopies that swallow-up UHF signals from satellites.

I still have a Garmin GPS-60 that I especially like because it is bright yellow. You can't drop such a thing in the pine-needles and lose it. (A very important consideration for a tool that you're using to confirm your map-and-compass skills.)

Forgot to mention; try to get GPS handhelds which support multiple satellite constellations. One that uses U.S. GPS as well as Glonass satellites. The more signal sources, the better your fix. Looks like Juniper sells one, their Archer 2 Geo model.

You could go crazy and try to find one which supports Galileo and BeiDou, but I'm not sure they have enough sats up yet. I've heard that BeiDou is only now available to Pac region and won't be global for a few years. I think Galileo is still in the testing phase.