Over my years of boating I have used two stroke engines and engines that required oil that cycled through the engine in its own separate system. I have learned that there are definite advantages and disadvantages to each type of oil cycling system. The main problem that I have found with a boat with an outboard that has a separate oil system is that oil changes can be a lot more difficult.
With two stroke outboard motors, I have found that one difficulty is having the Mercury 2 cycle oil that I need at the same time as I run out of gasoline. This can sometimes mean bringing the 2 cycle oil with you and mixing it in with the gasoline when you are actually at the marina. Forgetting your 2 stroke oil at home means that you might have to make a costly trip to the marina store.