I don’t think anyone can “sell” you on either boat. They are both great boats with some differences that may or may not matter to you or your family. We spent some time on each and it didn’t take long for us to decide which one we wanted. You should do the same. With the kids. Here are a few of the factors that helped our decision.
We overnight often and spend weekends or even longer when I can get time off from work. I’m 6’ 5”. The V-berth in the Express is rounded at the corners and I don’t fit. The Marlin’s starboard side of the V is longer and that’s for me. We bought a king sized memory foam mattress and cut it to fit. We roll it up and stow it when not in use. We sleep better on board than we do at home! I guess Ocean Motion… BTW, I can stand up in the cabin without a concussion but not the head. That’s for her anyway!
I do fit in the mid-berth flat out but it is not easy to exit especially you are the “inside” occupant. I’m assuming the berth is the same on both boats. We’ve had overnight guests on board and it’s fine for a night for them. IMHO, It would be perfect for kids.
The Marlin is a walk-around. This is better for us and our dog who loves the scenery up front while we’re slowly motoring along and while fishing or whale watching, I wouldn’t feel comfortable with her, or any kids for that matter, going up there on an Express. While boating at night we block the walk-around with fenders.
The helm arraignment on the Express is a plus for some, probably more so for a small family but for us, just me and the Admiral, two seats on the Marlin are perfect. I’ve heard/read that the Express helm can get a bit crowded???
Last summer, we had a transient Express a few slips from us. I could be wrong but it seemed to me that the cockpit area is a bit smaller on the Express. Probably due to the fact that it has a bigger helm area. On the Marlin, there’s plenty of room to spread our dive gear or fish 4 without rubbing elbows. At the dock, we have deck chairs and a table. And if the weather turns, they go home. Perfect!
My wife likes the windows in the cabin on the Marlin. Not a big deal for me. In New England we don't use the AC all that much except in July and having windows helps open up the cabin with a breeze and a view.
There are plusses and minuses with either model depending on what your priorities and uses are going to be. We chose the Marlin. There was a post a short time ago and the subject was similar. They had a grand idea that I’m sure will never happen. A walk-around using the 33 Express hull. Bigger, wider with lots of helm seating! Another vote for the SWORDFISH!!!!!!!!!!!