Disadvantages of rudders:
Heavy
Expensive
Drag
Potential big hole in boat
Linkages, etc. clutter up spaces
Maintenance
Fouling
Hard working AP
Let's stipulate two things:
Both engines are used all the time
If an engine goes down, there will be a way to steer (get home rudder?)
As I reread through the OP's first post and, considering each of his listed disadvantages both separately and then as a whole, I fine I'm questioning several things:
Heavy--really? The bigger the boat the bigger the rudder but, comparatively as a percentage of the overall weight of the boat, the weight of the rudders is tiny.
Expensive--same thing here. Really? When compared to the cost of a boat?
Drag--similar thing here. We're on a trawler forum where they move slowly through the water and we're even considering the drag caused by rudders? Really? It's that drag through the water that makes them work.
Big hole in the boat--yup. I'll give you that one. Probably two big holes.
Linkages--aren't those usually tucked way back in some inaccessible space in the stern? What else would you use that space for, 'cause on most boats you can't really get to it easily.
Maintenance--yup. Just one more thing to check on and lube when doing routine maintenance.
Fouling--if whatever is going to foul on the rudders makes it past the prop(s) I guess it might foul on the rudders, but all it's going to do is drag through the water and possibly make the rudders a little harder to turn.
Hard Working AP--maybe, but how are you going to use an AP if you don't have rudders. Is your AP going to adjust your throttles to keep you on course. If you didn't have rudders you probably wouldn't have an AP.
I recently had one set of hydraulic shifters go out and that prop (starboard side) was stuck in reverse. Because I do have rudders on the boat I was able to go into a lock and get tied up, then exit the lock and make it about 15 miles back to the marina. Without rudders I'd have been stuck with one engine and no way to use differential anything to get anywhere.
Thanks OP, but I'll keep my rudders.