My opinion is that The Boathouse has better food at a better value, and it has a livelier atmosphere. We loved the outside seating. The wine list is good and wines are reasonably priced. Service is very friendly and efficient.
We found Paddlefish to be a bit more formal, and the servers were nowhere near as personable as the ones at The Boathouse. The food was good, but quite expensive for the portions, and we are pretty light eaters. If you’re planning to order appetizers, entrees and dessert portion size would not be an issue. The wine list is more extensive than Boathouse if that matters to you.
Whatever you decide, let the restaurant know in advance that this is a special occasion, and since ambiance is important, speak up immediately if the table they give you is not what you want. Restaurants differ on what they will do for celebrations because someone is always celebrating something at Disney, but I’ve seen too many reports of people unhappy over things that could have been corrected if addressed at the time.