Howdy Doug,
Welcome aboard!
Well, you've gotten a lot of responses but you didn't say if you wanted comparisons between brand new (CARB compliant) big HP 2 and 4 strokes or small carbureted 2-strokes and similarly sized 4-strokes.
Everyone pretty much gave the "old" narrative. which used to be true.
Nowadays, the EFI 2-strokes meet CARB requirments and can be used anywhere. BRP claims the Evinrude ETEC will use "less" oil than a similarly sized 4-stroke engine (when you consider 4-stroke oil is "used" when you burn it and change it!!)
If you consider the small Evinrudes, 15hp or less, they're 4-strokes. (Manufacturers will be eventually discontinuing 2-stroke small carbureted engines in the US and more areas are banning NON-EPA carbureted 2-strokes.............. It doesn't appear that Evinrude, Johnson or Mercury sells carbureted 2-strokes in the US anymore))
The Evinrude 4-stroke 9.8 weighs the same (81.5lbs) as my Tohatsu 9.8 (in fact the Evinrude looks suspiciously like a Nissan/Tohatsu engine!!.....wonder why.......)
The Mercury's look like Tohatsu/Nissan engines...... (because they are!)
The 15hp 4-stroke Evinrude weighs the same as a 15hp Tohatsu.....(looks the same too.....hmmmmm)
The 15hp ETEC weighs about 180lbs. You're not going to lug that thing down the hill! (it's 60lbs heavier than a 15hp 4-stroke Evinrude/Mercury/Tohatsu and almost 100lbs heavier than a 15hp 2-stroke Mercury)
So, you might be a tad more specific. Are you asking if you should choose a small used 2-stroke?
I asked that question when I wanted a new engine for my 10' Zodiac Zoom inflatable. I had a 1977 2-stroke 6hp Evinrude "Fisherman" that pushed it pretty well, was very light and fuel efficient.
Mixing gas and oil was a pain, and I had to throw away what I didn't use after Summer, and I was worried that the lakes I use it in would eventually ban it, so I sold it for about $300! pretty good price.
I bought a new 9.8 Tohatsu 4-stroke. It's about 30lbs heavier, pushes that little Zodiac really well, uses even less fuel than the 6hp 2-stroke did and I just pour the left over fuel in the car!
If I was going to get an engine for a larger boat (25+ HP), I would get an Evinrude ETEC.
For a 15hp boat, I don't think I would get the Evinrude ETEC. But I would have to try one first I guess..but for the higher HP engines, It would be the ETEC hands down!
Cheers,
Rick