Bike based - GPS map 60 csx.
I finally replaced my Etrex legend CX with the Etrex 30. (It has the barometric function as well in my mind worth the extra £40 over the 20)
It has a weird software interface, trying (and failing dismally) to make it more user friendly for different scenario's, in reality this feature is a gimmic, recreation and Automotive are about all that are practical to use
The Etrex 30 is extremely accurate and perfect for any hiking based activity. Not had the opportunity to sync it to alternative maps yet, just using tracks4Africa, and Garmins European City navigator. Will be looking into some ordnance maps next, and then photographing converting some of my old maps into electronic format, but thats another project.
My Dad has an older GPS Map60 and it really is excellent where you have 12V charging ability, and then for an all days hike / kayak trip.
I took the etrex up Kilimanjaro in June 2012. Its awesome. Didn't miss a beat, despite basically being strapped to the shoulder of my Rucksack the whole way up Kili, and on for at least 8 hours a day - used only 2 sets of AA batteries (Sanyo eneloop xXx).
I know its a well trodden path, but knowing the altitude and distance to go gave me a massive mental edge over those without any idea of where they were, how far they had come / how far they had to go, I also know where I saw a Lammergeier, and where I took various photo's (cross referenced to the time/date)
It took me over 1000kms off road in Kenya when I could have been on a crappy "Tarmac" road. it deffinitely gave me the ability to go where I would not have gone without the GPS. Most practically, I was camping in very very high Grass south of the sand river, so having the GPS meant the difference between going to my tent each night and, well sleeping in the back of an 88 inch Landy.
My opinion is that for a motorbike based adventure the GPS 60CSX is the best bet, and worth the extra £££'s. Off the bike its good for three days hiking, on bike the (marginally) larger display is much larger! But the unit is still small enough to quickly chuck into a pocket when off to the dukas.
GPS 60 range rather than the GPS 62 because the 12v power connection is much more rugged and suitable to an offroad / motorbike environment. (if you can live with the 'slightly' reduced functionality no camera no wireless transfer etc) As a navigation device it is more suitable.
I chose the Etrex, because I do multiple day hikes where the extended battery life makes a big difference to me. this is where it is of primary importance to me.
Weight is a factor, but its more the smaller form factor that I find practical. I have another Garmin for the Car, but on my bike use the Etrex 30 in a RAM mount, and dont need anything better. I have no regrets at all, nor would I change
For vehicle navigation the "beep" to indicate an approaching turn is rarely heard on a bike, so you have to keep an eye on the GPS. I find the distance to next the most useful way of 'listening' but adding these data fields reduces the screen size, I usually only have two fields
Try the display and make sure that you can read it from your seated distance to where you will mount it. This is the same with the Etrex and the GPS map 60/62 as the displays are small, make sure you can see them at a glance and get the information you need. Being small they dont take up much of your field of view which is great.
Vibrations are a frustration, I have mine mounted on the single cylinder Yamaha XT660 Tenere, (mount bar behind the screen,) and notice significantly more vibration than on a BMW twin handle bar mount (theres a surprise) its only a problem for me at around 3000 rpm.
Practically my old Garmin Streetpilot 3 was easier to read with a much bigger display, as is my Nuvi 50 (again larger screen) But neither are anywhere near as suitable.
Those are my thoughts - but take it in context to your chosen use.