Good morning Matt,
I noticed that your vessel's name is "Little Wing"...mine's "Blue Wing" ...might be cousins
The primary difference between the A and the B engines is that the A model has a starter/generator hybrid, whereas the B has seperate starter, and alternator. There is a guy in our marina with an A model in another brand boat, and he likes it alot.
One irritation however...the Volvo turns the prop counter clockwise, opposite the original Atomic 4. My boat has an offset shaft (a factory experiment I guess, to compensate for torque from the original right hand turning engine.) There are some discussions about shaft offset on this board. This creates an excessive tendency to veer to starboard under way, and subsequently, requires a lot of extra force on the tiller by the helmsman (me) to compensate. I probably loose a knot or two in drag alone. You may not have that on your boat and I would be very envious. Fortunately the little engine is miserly on fuel consumption.