I'm not too worried about the 10 lbs, more of the vibration at the tiller from the 2 cylinder vs. 3 cylinder at idle. I've seen some videos and idle driving you get your hand shaken pretty bad. Also, the Yamaha is really a souped up 20 hp where the Suzuki is a down rated 30 hp.
We have the Suzuki 20hp. While it is a different engine than their 25/30hp, it is 2-cylinder and doesn't shake or vibrate much at all. At idle, you don't even know it is running. Our previous Honda 15hp 2-cylinder was the same. I'm surprised the Yamaha 25 vibrates so much.
I can say this about the Suzuki - it sips fuel. If the throttle is held at constant speed, the computer leans down the fuel supply. Since Yamaha now seems to have caught up with Suzuki in EFI outboards, I suspect it will be a similar miser with fuel.
Take it from a fellow catamaran cruiser - don't be lulled into "its only 10lbs more...". As your cruising years progress, those 10lbs add up without you even knowing it. A spare here, a tool there, an additional pot or two, some stuff that seemed like a good idea at the time - it becomes like boiling a frog.
We recently got a new boat. We sold the old boat with all the gear and spares and most galley stuff, and only took off personal items and tools and a bit of special cooking things. We took 4-5000lbs of this stuff off the boat. The waterline rose 5". There was stuff we forgot existed stored away in places we forgot existed.
But it is only 10lbs, and you will know where it is stored, won't forget about it, and use it often!