[...]Since I have moved from the Etrex 30 unit to the 64s[...]
Software and Performance
The biggest reasons for me upgrading to the 64s was the speed and performance of the processor. No specific details are given from Garmin on the internal hardware characteristics, but in comparison to the current Etrex lineup, the speed of map scrolling, which is a very important function, is virtually instant, or continuous on the 64s, whereas the Etrex has a very long pause (many seconds) before the screen refreshes and shows the new map locations. This map scrolling speed was faster when either travelling or when using the cursor to explore regions of the map not currently on display.