I have the Globalsat BT338 - love it - 17hr on battery - quick fix.
Best place for this conversation, though, is
www.gpspassion.com - they are really in depth there.
Almost all GPS units are the same, difference in Chipset with SiRfIII being the cutrrent tops. As to GPS software, each has its qualities, again, GPSPassion has some in depth articles on both units and software.