What features are important for a particular use are a very personal thing.  And..  The features needed for hiking are a bit more extensive (and a bit different) from those needed for automobile navigation use.  Below are my "essential hiking feature list" of GPS receiver features.

(I omitted features that are present in ALL receivers.)

1)  "Map" screen (as opposed to just a numerical lon/lat position fix):  Makes it much easier to see where you are relative to reference waypoints.  
2) WaterProofness:  Unit should be rated submersible to protect it from getting wet.
3) Long battery life:  Keeps you from having to carry so many batteries.  Some units with 2 batteries have longer life than some with 4.
4) Built in Maps:  Not absolutely essential,  but big help in orientation and estimating distance to nearest roads.  We now consider that any new GPS purchase should be one with mapping capability. 
5) Route capability:  Twenty Route capability is pretty standard, some have 50.  Make sure you get one with at least 20 routes.
6) Waypoints:  500+ user entered waypoints are pretty standard, some can store many more.  Make sure you get one that can store at least 500..
7) Multiple Datum capability is pretty standard:  Make sure all the datums you will want to use are included in the GPS you select.
8) Fit nicely in your pocket and lightweight:  This is a very personal thing,  but you should consider it when you are thinking about hauling a unit around in the wilderness.
9) Bearing to next waypoint:  Almost universal,  but essential to hiking use.
10) Screen Size and your ability to read it are important especially if you have problems with viewing fine detail.  B&W screens are fine for hiking and many color screens are hard to read in direct sunlight.  TransReflective Color screens are the exception.
11) 12 channel parallel receiver system:  Needed for best reception in difficult terrain and tree cover.

Not ABSOLUTELY essential features,  but nice to have.

1) We recommend map memory of at least 20 megs for a mapping GPS.  A minimum of 8 megs of map memory is recommended though you can "get by" with 1.4 megs or so if local topo maps for hiking maps are your only need.
2)  Transreflective Color screens such as in the Garmin G-60C, G76C and Vista/Legend Color models are easy to read in bright sunlight and are also reasonably easy on battery life when the screen backlight is turned on at night.
3) UTM  and MGRS readout may be a consideration for some.  This feature is available on a limited selection of consumer GPS receivers.
4) Topo Maps uploaded into your GPS:  The Garmin USA Topo CD maps contain contour lines and small stream data very helpful in navigating in off-road territory.  Magellan has a new TOPO map offering which is not quite as detailed as the Garmin offering.
5) For use under heavy tree cover or difficult (multipath) terrain conditions,  an external amplified antenna will generally be helpful.

Detailed Product Reviews for the following units can be found in the FEATURES page HERE.  In no particular order,  SOME of the current 12 channel parallel GPS receivers WE consider most suitable for hiking use include:
A) GPS receivers WITH the ability to upload maps into the GPS from optional proprietary maps:
Magellan Meridian (basic/gold/platinum)(^), Magellan Sportrak Pro(!), Garmin GPS-60C(@&^), GPS76CS(@&^), GPSMap76(@&%), GPS76C(@&^),  Vista Color(@!), Legend Color(@!), Vista (@!), Legend(@%) and Lowrance iFinder(!#) (all models).

PRODUCT REVIEWS of all above models can be found in our FEATURES or GPS PRODUCT REVIEWS sections of our website HERE.

B)  GPS receivers WITHOUT the ability to upload maps into the GPS:
Garmin GPS76(&), G-12xl(@&#), G-12CX(&#), G-II+(&#), G-48(@&#), Venture(@),  Magellan 315, 320

(**) The  standard eTrex and eTrex Summit have a substantially reduced GPS feature set as compared with competitive models and while we think eTrex and Summit are "cute" and accurate enough in position measurement,  Our opinion is that other models just slightly more expensive provide the needed feature mix for serious hiking activities.  This comment does NOT apply to Venture, Legend, and Vista  models.
(#) While these units are not "obsolete" from the standpoint of technology,  newer units with more "features for the money" are recommended.
(&) Units which have a "standard"  external amplified antenna port. (may be 2.5v or 5.0v power, check before buying antenna)
(@) Units which have the ability to calculate area (acreage) after you walk a closed loop.
(%) Units which have (only) our recommended minimum 8megs of user loadable map memory.
(!) Units with 19megs to 48 megs of non expandable map memory
(^) Units with 49megs or more map memory or with optional plug in memory modules.

Units NOT suited to serious HIKING and GEOCACHING use due to being designed for other applications:
Garmin StreetPilot,  ColorMap, StreetPilot  III,  StreetPilot 26XX(all models), iQue (all models),  Magellan RoadMate(all models)
TomTom GO
Delorme EarthMate/SA9 system
Etak Skymap systems
Rand McNally Systems
(Any system requiring a laptop, palmtop,  or ancillary computer device other than for data and map loading.  A GPS receiver for hiking should stand alone in the field.)

Notes about GPS receivers for use in the woods:
1) eTrex models (due to their small size patch type antenna) have slightly less antenna gain and sensitivity and may not perform quite as well as others in difficult receiving conditions.  They work just fine "out in the clear".
2) Helix type antennas tend to get "detuned" and have lower sensitivity if the antenna is placed close to a metal surface.  Some detuning can result if the antenna is placed in a pocket or in a knapsack with metallic items or your body in close proximity.  Patch type antennas suffer less and work better if you want your GPS to receive with the unit close to your body or in your pocket.  NO GPS will perform properly in these conditions unless it has an external <maybe amplified> antenna out in the clear.  GPS receivers are DESIGNED to operate properly WITH A CLEAR SKY VIEW.  Any time you compromise with less than a full sky view,  you are compromising the operation of the GPS and the accuracy of your position fix.
3) There is NO GPS which can be trusted to perform at all times in heavy tree cover or in steep and narrow valleys where GPS satellite signal masking can be present.  If one GPS performs today and another does not perform tomorrow in "identical" circumstances,  it proves nothing without further testing.  The GPS satellites MOVE continuously and today they may be in an excellent position and tomorrow when you test they may be in a quite poor visibility situation.  Except for the eTrex models noted above,  there is little difference in "in the woods" performance between the various models recommended.  We did  find that the Sportrak Pro models gave slightly better performance under tree cover than most models.

Discount Internet GPS Vendors> HERE
(Note:  Joe and Jack do not permit vendors with unresolved customer complaints that we are aware of  to advertise on our website.)

Note:  If you have a suggested units that you think should be added to my list,  please let me know.  If a particular unit is not listed, this DOES NOT mean that it is deficient in design or manufacture.  It simply means that Joe and Jack like the listed units slightly better for this application.

Email to:  Joe Mehaffey

Dale Depriest has more suggestions for picking out your first GPS receiver, CLICK HERE

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