Also posted on the other thread.....
Depends whet you want from the Unit....
The GPS part is performance wise about the same across the units, it is how this is dealt with.
The Edge is a nice piece of kit, and shows a simple line route which can be followed, simply turn as you reach the change in the line, it is the depth of recording withheart rate, altitude, and others that make it a GPS assisted bicycle computer. The bad news is that it records in unique format which can be a problem with some navigationg software, and require third party conversions.
The ETrex is similar, in its basic form the mapping is similar to the Edge but will beep and indicate turns... With the more advanced there is basic mapping.
The ETrex and most others record in a standard format compatible with most mapping software
The "ultimate" at the moment and the only one which uses
Ordnance survey is the SatMap Active 10.
Note that in all cases the mapping is strictly controlled and not transferrable.... so you need to calculate in maapping costs as well.
It is possible to plan on Bikely or other free route planners and download/ display on Google Earth or the free routing However to get the best you will need to get Tracklogs / Anquet / Memory Map to map on the PC.
My advice would be to get into a shop and look / handle these units - see what fits your needs best and then give some strong hints.
Finally - mounting is personal, but all are "handlebar based" and need a handlebar orientated mounting on the bike... I use a SpaceGrip for this- however boom based makes the unit too far away to see the mapping or detail.... try readingthe small print on the frame label and you will see what I mean. YOu also find yourself contorting in awkward positions to operate any controls....
On the Catrike and Street Machine I filed out a rubber bung and fitted the unit to the ridged unit of the Mirrycle (I see you have these fitted!) whch places it in an ideal position to initially see, but secondly to operate the functions.