This may well be a question for a dealer; since they would have the latest information on improvements to the model and any additional equipment included in the standard package!
This is a great user forum, it helped me get started quickly in terms of maintenance, modifications and improvements and of course, how to sail these incredible boats. I believe the majority of members sail either mod 1's or 2's and a few 3's.
I have a 1989 Mod 2, and it is air tight with the box in place. It doesn't have as much storage as the Mod 1 and 3's. Good news, is that I have capsized and once turtled and it has never taken on any water. My friends with a Mod1, capsized and turtled, the front hatch wasn't shut and the boat filled with water and nearly sunk. I have considered removing the box on mine for more storage, but I'm still nervous of flooding it after watching the other boat that one time.
Mod 2 is a great dry capsize boat. Faster than the mod 3 but less forward storage. If its a good boat for the right price buy it. Cars and houses are great for storage. You could always remove the bow box and have a wood hatch like the mod 1 if you wanted.
I know some folks need the extra space for a trolling motor battery and such, but the amount of storage space in the Mod 2 seems adequate for the average sailor. There's plenty of space for a couple of fenders, a collapsable paddle, some extra line and a dry sack of sundries. Unless you really need the extra space, I'd look more at the overall condition of the boat, price and the like. If it's a nice boat for a good price, I'd probably go for the Mod 2, but that's me.