Don't choose on the basis of hardware alone. Software is just as
important...Garmin Bluechart or Navico or C-Map????

I think C-Map NT is unbeatable. You can use it at home on your PC and then
upload routes etc to you plotter. If you check the C-Map site you will see a
list of compatible plotters. I use a Navman 5600 - very good except for
mounting bracket - better to flushmount if possible.

Mike