12 channel parallel processor

These are must-have features, which are standard for current GPS models

At least 20 routes

At least 500 waypoints.

At least 1024 tracklog points.

Newer GPS receivers should have upwards of 2000. The larger the tracklog capacity, the longer the trail that may be recorded into the receiver's memory, and the higher the accuracy of the tracklog.

Battery consumption

Newer GPS receivers can last as long on only 2AA batteries. Generally, the more basic units will have lower battery consumption than the all-bells-and-whistles models.

Mapping

Some GPS receivers have the ability for you to upload a proprietary map database into your receiver. This is not especially useful for mountain biking or in the jungle because the maps only show main roads. Besides, if you can upload tracklogs of trails into your GPS from your PC, there's no need for this mapping feature.

Barometric altimeter

Barometric altimeters provide much better accuracy over the GPS-calculated solution for elevation. But the price difference between an eTrex Vista (a model equipped with a barometric altimeter) and an eTrex Venture is about RM850. You can buy a Suunto Vector wrist altimeter for less than RM500. (If fact, you can get TWO Ventures for the price of a Vista!) However, one useful feature is that the Vista attaches altimeter values to its tracklog data. So you can have countless hours of fun calculating altitude gain and plotting the elevation profile of your rides. (Nerds rejoice.)

Electronic compass

Let's see� a compass that you have to calibrate, relies on batteries, and competes with the GPS for power. If the GPS receiver breaks or is lost, your compass will be gone too. No thanks. A good magnetic baseplate compass costs RM50.

WAAS

Wide Area Augmentation System (European equivalent: EGNOS). Improves the accuracy of the solution. Groundstations with precisely-known locations receive GPS data from the GPS satellites to check the data for errors, and re-transmit correction messages to a WAAS satellite in geostationary orbit, which in turn retransmits the correction to GPS receivers. Although Malaysia is covered by the footprint of Europe's Indian Ocean Region Inmarsat, it's not clear to me whether WAAS-enabled receivers can utilise EGNOS correction data.

In my experience, my non-WAAS enabled 4-year old GPS12 is accurate enough for recreational use, so I wouldn't pay extra for this feature.

Waterproofing

Newer GPS receivers can survive brief accidental immersion.

eTrex Venture

Relatively cheap, very compact, comes with PC cable, takes just 2 AA batteries

Antenna sensitivity and bicycle mounting system issues

Magellan Sportrak

Sensitive quadrifilar antenna, floats, 2000-point tracklog, takes just 2 AA batteries.

A little bulky, basic Sportrak doesn't come with PC cable

Magellan 315

Sensitive quadrifilar antenna, floats, takes just 2 AA batteries. Good buy if you can get it cheaply.

A little bulky, doesn't come with PC cable. Tracklog capacity, at 1200 points, is a little small compared to newer units.

Garmin GPS76

Sensitive quadrifilar antenna, floats, 2048-point tracklog, takes just 2 AA batteries.

Bulky, reduced antenna sensitivity when unit is held horizontally

Garmin GPS72

Similar to GPS76, but will be cheaper!

Not yet available at time of writing, bulky, antenna may have same issue as GPS76

Garmin Rino 110

Unique two-way radio function and peer-to-peer position locator

Not yet available at time of writing.