The Donzi is going to have a nicer build quality. The fit and finish will be nicer, as well as some of the rigging. That said, the Baja's will probably be a better ride. They are larger, heavier, and they don't have a stepped hull. Remember, the Donzi isn't really a 26', the swim platform makes it more like a 24'. The 29' OL vs the 25' OL is going to be a night and day difference. That 4' is going to feel like a mile.
IMO you should look at the following as well:
I wouldn't worry so much about actually "breaking" a motor on a twin engine setup, as long as you're fairly easy on them they're pretty reliable, but the maintenance is going to be double. Buying 16 spark plugs, two sets of wires, 16 Q's of oil, double the drive lube, two oil filters, two fuel filters, etc. adds up in a hurry...