My view on GPS units is greatly swayed for how I use it. This may be long and bit thrown together (disjointed).
I need something that has a good antenna, simple, weather proof, run on alkaline batteries, b/w screen, WAAS (for when those stations come online in the continental interior), at least 500 waypoint memory and last price.
For hand held GPS, I prefer the quadrapole antenna vs. the patch. Over the years I have found that they give a bit better performance, especially with issues seeing the sat. constellation (canyons, trees, etc). For general use it is less of an issue.
I like alkaline batteries because you can pick them up anywhere. In cold conditions you can keep a set in your pocket as well. When I am working, I transfer batteries out of the unit once it reaches ~50%. Power in the unit does effect performance. I then use those batteries for flashlights, iPod, etc.
I prefer b/w screens. They use less power and are easier to see in direct sunlight.
I like a portable handheld for collecting data in the field. I don't need a big screen or loaded maps for navigation in the field as I always have a paper map for that that.
For in the vehicle navigation I use a laptop. The screen size on the handhelds are just too small to navigate, especially as the driver (I don't do this in traffic). I use an old Mac G3 Powerbook "bronze" laptop. I am not happy with this set up as the laptop takes up too much room if there is a passenger. I am looking into getting a ~7" touch screen LCD monitor (like the Lilliput). They range in price from $150-$250. I can then operate the laptop mounted under the DS seat (maybe) in clamshell mode with an integrated
trackball&keyboard. If I were getting a dedicated computer for the car, I would make sure I was WiFi and bluetooth enabled in order to give greater mounting options.
Those are some of my thoughts on this topic. I have thought alot about this and been researching it though my presentation is a bit goofy.
Ross