From everything that I've read, the m/c rags all say that the Roc has a slight edge over the Suzi in performance, problably not enough for the average rider to make a significant difference.
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.
Not long after Mr. Max's debut, Kawa introduced the Eliminator as an answer to the Yam. It took the route of big ass rear end on a lowered front much like a jacked-up hot rod in the late 60's. The Suzi reminds me of the Eliminator. Plus it looks like it could be in a Jetson's cartoon.
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.
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