Fishone,
You and I are in the same boat!
I've been looking at these two as well trying to decide. For me, kids come in to play (7,3,1) as well. I spent a good amount of time on each at the boat show.
I'm not sure why, but I also think the Marlin cabin feels bigger. Maybe its not as full of stuff... I don't know.
For me, I will only have a few overnights each year with the kids and maybe my wife so I think both are large enough. I really like the Marlin's access to the bow for fishing and for my kids. It adds another dimension for them as we will spend time anchored/rafted up where it is usable.
I didn't see any difference in the transoms, in fact I thought they were identical??? Maybe the pre-04 Marlin is different in that it doesn't have the drop down bench.
I do like the helm seating in the 305, but I like the overhead boxes/net in the Marlin.
I think for me it is the Marlin, now just have to figure out how to pay for it!!