I admit I like my four stroke. Mine is a 50 HP. Comes in at about 200#. I always thought my boat was a little stern down at rest. But up and running the power trim makes a huge difference. Fuel efficiency is pretty darn good. Less hassle. Clean. I read they are mechanically more complex, but that is beyond me.
Sounds like boat trim is going to be your primary concern.
More complex for sure. The guts of this Merc are taking up half of my shop. It is, in essence, a 1.7l DOHC car engine turned on end with a remote oil sump.
More complex is subjective. Some of the two stroke engines are less complex--but the key word here is the engine. Remember there is more to an outboard than the engine. On some of the ETEC's (and others) they have high pressure direct injection; basically a crude version of what modern cars use. So then you have a very complex fuel system that feeds the engine which is controlled by electronics that were designed and programmed by people. In this case that's where the 4 stroke is much more reliable in the long term. The technology of a 4 stroke DOHC engine has been around for about 100 years and has been proven. Yes there are more parts. That doesn't mean they're less reliable because they have more parts. It just means they have more parts inside the engine. Big deal. A 32 valve V8 automotive engine will have 32 valves, 64 springs, 64 keepers, 4 cams, 2 or 4 chains (or sometimes a belt), 8 pistons/rods/pins, 16 clips (sometimes), bearings, oil pump, gaskets, etc. By going off of the numbers of parts inside, OMG they have to be unreliable because there's more ways for them to go wrong. But in reality, they run for hundreds of thousands of miles (tens of thousands of hours) when properly maintained. Most of the time any damage to them is operator or owner incurred.
Similarly, most of the time a 2 stroke engine damage is operator or owner incurred. In other words, forgot to put oil in the fuel, let the gas/oil mix sit for years and foul jets, run lean, destroy cylinders, or sometimes let them sit and they get dirt dobber nests under the cowling (no air filter), fire the engine up and take off...eats dirt...self destructs. Or in the case of high pressure direct injected engines such as etec and some yamaha 2 stroke, they're real sensitive to fuel and real sensitive to poppet valves & thermostats. FICHT is similar, IMO FICHT is garbage but that opinion is based on working on FICHT jet ski's. Again, sensitive--or more sensitive than a comparable horsepower 4 stroke.
Downside to 4 stroke of larger HP is because of more parts, IF something goes wrong, it costs a little more to repair. Thus, take care of your stuff.
The weight difference between 2 and 4 stroke is getting narrower as time goes on.
20 years ago a 4 stroke outboard was rare. Today around here it's about all you see. It's not because they're forced upon us, I mean new cars with better emissions are 'forced" on us yet a lot of us still drive old stuff, it's because they really are better in a lot of ways; one of which is a far superior idle quality and secondly they typically use about half as much fuel as a comparable 2 stroke.
Far as hour use, I'm sitting here looking at an F300 on a Sea Hunt 26, that has 4385 hours on it. If the average speed of a car were 45 mph, that would equate to just shy of 200,000 miles, just to give you an idea. I can't say I remember a 2 stroke with that many hours but most of the old 2 strokes didn't have hourmeters either.