It really all depends on if you want two-stroke(new tech -forget regular carb/efi engines!!) or four-stroke. Both have valid arguments, which is better is entirely up to the owner?
Personally if it were me, I'd find it very hard not to be considering the 115 Optimax.
Sure the 4-strokes will be quieter, although at low speed there's not much between them, its only at high rpms that you'll notice the difference.
Don't leave anybody tell you that fuel consumption is better with a 4-stroke either, new-tech 2-stokes (optimax, etec, ficht, hpdi) are just as good on fuel and can be better in some instances.
As for performance, well the 115 Optimax will easily win this one, being the lightest engine here and also being 2-stroke. The only other that will give it a run for its money would be the 115 ficht (theres no 115 etec or hpdi yet!!). As for the Honda being the most powerful due to its displacement, it weighs 225kg (thats the same weight as a 3.0l V6 Optimax!!)
If it has to be a 4-stroke then go with either the suzuki or yamaha, at least they've made some attempt at keeping the weight down.
hp/ton
Honda4............511
Merc Optimax....676
Suzuki4........... 605
Yamaha4..........592
Evinrude Ficht...676
Evinrude etec....688
The Etec 115 isn't out here yet but it would certainly be worth waiting for, will be quieter and more fuel efficient than equivalent 4strokes not to mention no servicing for first 3yrs.
I will say that the above is biased as I will never buy a 4-stroke engine, I prefer to hear the exhaust note scream and the kick in the back feeling you get from an opti when floored
. It will always come down to personal preference though, but I will warn you about those hondas- they're big heavy and slow and there are better alternatives!
also the Throttle response is much more sensitive on the 4 stroke than my current 90 2 stroke (yamaha)
i have driven a 18 ft whaler with an optimax on it and that flies too 
