Just pointing out the differences here. Please don't take is as a personal attack on whichever unit you own.
The Geko and Etrex H don't do mapping the Legend HCX does and it has a colour display which displays the topo maps properly It's easy to read in sunlight and has longer battery life than the monochrome model it replaced.
The Geko and Etrex H do 125 waypoints per route the Legend HCX does 250. I find this feature very important. Your mileage may vary.
The Geko doesn't have the high sensitivity receiver. It will lose signal in woods and deep valleys. I own the Legend CX and it does this.
H=high sensitivity C=colour X=micro sd card slot
Barometric altimeter and magnetic compass on the higher models reduce the battery life when turned on and I don't really see the benefit