According to the Garmin web site, the Edge 705 weighs 3.7 ounces and the eTrex Vista HCx weighs 5.5 ounces (with batteries). Both have the same 176x220 pixel screen size.

76cxs is 160x240 pixels and 7.7 ounces. It is physically much bigger than the eTrex (4.2x2.2" vs. 6.2x2.7").