You might want to go the the Seven Seas Cruising Association web page
www.ssca.org and do a search on the discussion board. A bunch of folks
have recently had a long discussion on the advantages/disadvantages of
chart plotters vs laptops/software for navigation.
Only problem is the board seems to be non-functional for the last week
or so. It will be fixed soon hopefully.
Now that US charts are free it is probably cheaper to go with a
laptop/software and UPS GPS antenna IF you already own a decent laptop.
You might be able to set this up on a swinging platform so that you
can check it quickly if not exactly study it while at the helm.
I have a Garmin GPSMap 182 at my helm and I really like that. This
model is now out of date and you may be able to find one at a
reasonable price. The Garmin 2010 has a bigger screen and you can pick
up the monochrome version on eBay for $600. The only problem with
Garmin is that the charts can be expensive but I suspect they will be
giving US charts at low prices in the future.