I can vouch for the 4G Radar being low current draw and high resolution. [Our B&G picks up most ice and almost all crab pot buoys; rain squalls too if you tune them in...]
The RADAR overlay on a chart plotter is a powerful feature, and you don't need MARPA to accomplish that. [i.e., you can use a cheaper compass...]
When I analyzed our desire for separation of functions and redundancy I reasoned if I had one each chart plotter and radar screen, I still have no redundancy between functions- only separation and no integration. If I go with 2 MFDs, I have redundancy and optional separation and integration. [e.g., radar overlay, AIS, etc...]
The addition of WiFi and compass to enable radar overlay on the chart plotter are just under US$200/each; less than you would pay for a MARPA compatible compass alone.
I, and others more qualified, can provide specifics if you are interested.
Food for thought...
Thanks Bill and others for advice. All of it is indeed excellent food for thought.
I think if I were to replace everything, and didn't mind spending pots of money, I'd go for the Zeus2 and radar, and have my tablet as a backup chart plotter. Alas, where I am located the dealer options mean paying top dollar -- read never below "MSRP"-PLUS and high labor costs -- every time. For example, the local dealer wants at least $750 just for the two parts (expansion port and wireless module) to get wifi working on the B&G system (plus installation), and fully $1000 for the compass (which, as you point out, I could go without, getting the fancy GPS antenna with compass instead I guess, but no MARPA).
Has anyone actually seen the 3G and 4G in action? I wonder if the 4G is needed (it's at least $500 more). Here the 3G radar bundle is $2200!
Regarding the Furuno wireless radar, I have considered that. Has anyone used it?
One obstacle is that I really don't want to throw out stuff that works well (Yankee upbringing, I think). Integrating with my current instruments is really not a psychological option (they all work but they cannot be networked with new gear). This means that I would not be able to use any of the fancy "sail steer" (or whatever it's called) stuff on the B&G.