From my perspective, it comes down to your preference in the look and feel of the bike. I don't know how old you are but you may be able to remember back when Yamaha first introduced the V-max. It was the first true power cruiser. It had the massive engine look and high bars with the low rear-end. Much like a pony car of the mid 60's with the front end lifted. Gave it that "big-shouldered" look. The Roc follows that mold.
I prefer the "big-shouldered" look since it fits me better. Also, like TxRIIIRider said, it's a lot more versatile. I've got mine set up for touring but in less than an hour, the windshield gets shorter, the bags come off, and the touring seat goes to a single, thus completing the transformation from Joe Comfy to Billy Bad-ass.