Yeah, like has been said, it depends on what kind of riding you truly plan to do.
If you plan on going on a fair amount of freeway rides then i would say get a 1300.
If you are not going to be taking many freeways rides then i would say a 750 should be fine for you.
If you are going to ride 2-up a lot is another factor.
If you get a 1300 and don't ride on the freeways then you are carrying around an extra 200+ lbs when you don't really need to.
Its almost like riding a 750 with a grown passenger ALL
in terms of handling the Bike.
If you want a bike to commute to work (non-freeway) and mostly ride within a 100 mile radius then a 750 will serve you well and be a easy ride that is easy to maneuver/handle.
If you envision yourself taking a lot of road trips of 300+ miles while using the freeways often, plan on going to Sturgis etc, then a 750 won't cut it, imo.
I would not want to be in the position of having to do 70+ for hours on end on a 750, but that's me, i dont need the bragging rights or
the pain, i have far enough to brag about already