I also enjoy both types of fishing, and there are distinct advantages to each one.
When I am fishing along a river, or a lake, it is pretty laid back and relaxing usually, at least until a big fish grabs your line and heads out to the middle of the lake with it. Pretty much you know what kind of fish you are apt to catch, especially if it is a lake where you fish often.
Ocean fishing just seems to be a lot more interesting, since there are just so many fish that are a possibility of catching, and you just never know what type or SIZE of a fish is going to be on the hook when you get it landed.
However, you need a lot more expensive fishing tackle to ocean fish, at least if you are going to do more than fish in a small inlet where the larger fish are not going to be biting .
So, for someone like myself, with not much money to spend on tackle and nice ocean rod and reel, mostly lake fishing is the answer, unless I am fishing with someone who has all the equipment needed for the ocean.