When I first received my Garmin, I had both the GPS and the Cateye mounted. During a switch in bikes, I rode for several months with just the Garmin alone.

I have since remounted the Cateye because I found that, while very accurate over time, the Garmin is slow to respond to changes in speed. I notice that, for instance, as I start a descent, the Garmin might get stuck at, say 15 mph and stay there long after I know for sure I have to be moving at 25 mph or more. Suddenly, it will sense the change in speed and jump straight to 25 from 15.

With both units operating simultaneously, I find that, at times, the two agree exactly. At other times, they do not (and I assume that the Garmin is faulty). For instance, I cannot count on the Garmin to get an accurate reading of maximum speed attained. It is just too slow to respond. Not that the number is an important one, but, I like to see how fast I can get her going on downhills. The other day, my computer registered 49 mph max on a downhill run, the Garmin only 41.

I cannot really watch these two units on an extended downhill . . . too dangerous, but I have watched long enough to see the computer smoothly run through the numbers as you accelerate while the Garmin has yet to sense that speed has changed more than a mile or two per hour.

I don't know quite why that should be . . . but it is.

For keeping stats on a ride, however, the Garmin is hard to beat. It can accurately track your route, distance, average speed, time stopped, altitude, etc.

The unit can be set to calculate routes for different types of vehicles/routes . . . bike/motorcycle/automobile/pedestrian, on road or off road, freeways/toll roads (yes or no), etc.

The Etrex does have an odometer . . . but, since I sometimes use the unit in my car, the odometer reading doesn't relate to my biking miles or the miles on any one bike.

I have found that both units will act strangely at times.

Last weekend I descended a hill and checked the max speed on the Garmin. It was 174 mph. I'm just about to congratulate myself on having the computer as a backup when I notice that its max reading was 96 mph - so, whatever messed up the Garmin also messed up the computer (the computer is a wireless model).

Anyhow, both are great toys, and I love having both on the bike (the Garmin is mounted to the bar, the computer to the stem (or whatever you call that part that clamps the bar in place). The mapping features (as described by an earlier poster) are a great plus.

I say, if you have room on the bike, use both.
Caruso