Since you're looking for opinions, here's mine...

You didn't say whether the 2-stroke is a HPDI or not, but if not I'd
splurge for the 4-stroke. It might take a long while, but if you use
the boat alot it will eventually pay for itself in fuel and oil
savings. Even if it doesn't it will help with resale, and you get the
other advantages. I think Yamaha is your best bet in an engine choice
for reliability and resale. I can't comment on the Hydra-sport angle
or Key Largo quality first hand. The price doesn't sound bad for the
whole package.

Recommend you get a test ride in one with a load of fuel, gear and
people in the kind of conditions you'll be using it in before you take
the plunge - especially if you're worried about acceleration or top
speed with the 4-stroke.

FishFan