With regular 600 mile road trips, I'd definitely go with the Sporsters. It's not just that you're sitting upright with race seats like the Pole Positions, you're quite locked in from the shoulders through the hips and knees. Little room to move laterally in the seat, reposition your legs a bit, etc. You might be strict with your driving position, but I doubt you're as strict on those journeys as a fixed back seat would keep you.
With either option you'll need coding.
There is a school of thought out there that a race seat and standard 3 point harness (and sans roll cage) is not safe. Borrowing from another forum discussing the subject --
Race seats are designed to be used with a harness, not a factory 3 point. The factory belts are designed to work at certain angles across your body. Those angles change with a race seat. I dont care if it is NASA legal, from a safety standpoint dont do it. Wait for the bar.
The typical consideration for a fixed-back seat without a roll bar is that you lose the benefit of the factory seat back, which are often designed to yield (i.e., fail) in the case of a rollover in order to provide survival space. A fixed-back seat won't do that, so if the roof does crush in a bad rollover the fixed-back seat may not be your friend. That's frequently the logic behind not allowing a fixed-back seat without sufficient rollover protection.