Suzuki 800 or 1600 boulevard?

I ride a 1998 Suzuki vz800 marauder. I love it, but it Is not so great on the freeway due to it's dual carb set up. Do the new boulevards get better gas mileage? I think I want the bigger one, the 1600, not for power but for freeway cruising, my 800 is great on the surface roads, but it seems like it's at a high rpm just waiting for an overdive on the free way and I don't wanna change my sprocket ratio again, so the real question is, 800 or 1600? Sorry I don't know the new system as well I know it's c and some number of cubic inches which confuses me, its Japanese, I was told they are on the metric system.