Harry, first take into consideration what charts
you will be using. That may influence your decision. Though I'm not sure if all programs will accept all charts
or not. Just something to consider.
I use Polar View with the free NOAA charts for the US on my Mac. I'm very pleased with this low cost solution for my needs.
Polar View has an excellent color palette with the vector charts. It's not demanding on CPU or graphics resources and runs quite fast.
My second choice would be MacEnc.
is immature at this point on the Mac, but getting better.
Also, give very careful consideration to how you will protect your laptop
intrusion. Especially if you wish to have the nav software
up and running while underway. It's turned out to be harder than anticipated for me.
At this point it's clear I would have been wiser to go ahead and add a new chartplotter
at the helm
to replace an out of date monochrome Garmin
. Damn hindsight.