Cant compare Satmap and Garmin Dakota/Oregon as I concluded they were much the same and it came down to price in the end. So went with the best deal I could find. Some say the Dakota screen is difficult to read in daylight, but have never had a problem and dont know the satmap to compare.
I do find with the Dakota that I need something on my computer screen to plan the route on before downloading to the GPS; MM etc or some of the options discussed above are worth a try.
Oh and 15 hours + off rechargable AA batteries.