The advantage of a 4 stroke over a 2 stroke is really just that the 4 is quieter. In the new technology 2 strokes (HPDI and Ficht/ETec) the efficiency and emmissions are actually better on the 2-stroke engines in many cases. What size motor(s) are you looking at? I'd be very leary of the big block HPDIs. Yamaha has had some problems, not with all of them but with enough, that they still need to work out there and I've heard enough stories about blown power heads that I'd be leary. In a new tech 2 stroke, my vote would go to the Ficht. They DEFINITELY had some issues early on but agter Bomb bought OMC those got taken care of and the motors are solid.
The 4 stroke has a couple of disadvantages, in my opinion. First, 4 stroke engines don't really lend themselves to long hours of running at high RPMs like 2 strokes do. They last a long time in cars because cars have transmissions and you don't push the engine at 4500 RPMs all the time. To me, a 4 stroke on a boat is sort of like driving your car uphill at 4500 RPMs all the time. Obviously, this isn't completely accurate but you get the point. 4 strokes also have more moving parts and more things that can go wrong but they do get good gas mileage and are quieter than anything else out there.
2 strokes have come a long way in the last few years. I would avoid the Verado because its new and the first time anyone has ever tried boosting an outboard in a marine enviornment. Time will tell how well that works out but looking at the early Ficht, Optimax and HPDI experiences, I'd not want to be the Guinea Pig. Like I said, in a new technology 2 stroke, my choice would be the Ficht.
Now, having said all that, I have a plain old carbed 2 stroke on my boat and am plenty happy with it. I get 2 - 2.5 nmpg (not great but a whole lot better than they used to be) and if something breaks down I stand a better than 50% chance of working it out enough on my own to get back to the dock. The technology for the carbed 2 stroke is also bullet proof no matter which motor you get.
To answer your simple question, is not hearing your motor worth the extra money? You definitley aren't going to save $3k or more in fuel usage over the years to make up the difference between a 4 stroke and a direct inject 2 stroke...