I think you'll like the MacBook Pro - ours have been real troopers. Looking at the photo, it appears you have one similar to our 15", circa 2006. If so, it has a 2.2 duo core processor and probably 100 gig hard drive. The typical install had 1 gig of RAM; I think it was expandable to 2 (not certain on that). Ours has been with us on Wild Blue and in the RVs since we bought it. That model has a battery that will last 1.5 to 2 hours when new, so if you intend to use it on the boat, you will want a 12v power cord for it. Even though it is a durable machine, we have always carried ours in a padded case.
I have used MacENC for planning, but not while underway. Haven't used a GPS puck with that particular Mac, but I know others do.
Regarding the difference between GPS and simulated GPS that requires wifi: a GPS unit (or puck, or chip) will give your location regardless of any other connection, receiving a satellite(s) signal. To use it on your computer, you will have to plug the GPS (or puck, etc) into the computer, generally via USB. You will also need some softward to make the computer functional with the GPS. Thus, MacENC (there are others, too).
Simulated GPS simply uses triangulation from cell towers to determine your approximate position. You HAVE to have a cell/data/wifi connection for that to determine your position. I have no hands on experience with that, but it seems that it would not be a good solution for position determination while boating. You would need a wireless broadband card AND be where you can get a constant signal.
Hope that helps. Oh, and once you go Mac, you won't go back. :wink: Windoze machines feel clunky by comparison - that is an opinion from a dedicated Mac guy who has used both, not a statement of fact.
Best wishes,
JIm B.