I'm sure I'll be corrected here, but here goes, IMHO....
2 strokes are simpler and you're more likely to be able to fix things at sea if things are to go wrong.
4 strokes are next to impossible to start pulling apart at sea except for plugs. They are a lot more complicated and a lot more moving parts to go wrong.
2 strokes are also a lot lighter.
2 strokes can also be put down on any side whereas as 4 stroke has to be on one of two sides only or it'll empty its oil everywhere.
However, in my experience, 2 strokes have been nothing but problems. They are a lot heavier to turn over if it's a recoil start and a lot more thirsty for fuel. You also have to worry about oil mixtures if it's a pre mix.
Having had this 4 stroke, despite people telling me not to consider a 4 stroke for the size, I'd never consider another 2 stroke.
I went for my 4 stroke because while it was heavier, it was also younger, easier to start, quieter, more fuel efficient and I knew the history of it (as it was brand new). The problems I was having with the 2 stroke have disappeared and now boating is fun again. There's nothing more depressing than an engine that keeps dying on you or is a pig to start.
That said im sure I've had a very bad time with 2 strokes. There's thousands of people who swear by them.
There's a reason why they are used commercially and for racing.
Im sure it's just my experience with this one engine that's put me off