Tough call, they are both excellent bikes, and they are quite different. The Hyper is not really able to compete with the Multi on many levels of performance...power, handling and suspension. The Multi is really a better bike. That being said, the Hyper has it's place in my garage. It small, light, quick steering, and just plain fun to ride. I have both a 2013 hyper and a 2013 Multi. If I was forced to keep just one, it would be the Multi. I would be heartbroken, because I love my little Hyper.
Also, I previously owned a 2010 Multi, and the new 2013 is amazing in comparison. Absolutely flawless fueling, and the sky hook suspension is a technical revolution.
As to fit, I am 5'11" and the Hyper is just so easy to move around...not only around in the garage, but around on the road. If I want to make a quick u-turn, I don't even think twice about it. Dirt roads...no worry. With the Multi, and the extra ~90 pounds and extra height, I am definitely more cautious when maneuvering. Both bikes are brand new, and I'm sure there is some "fear of a tip over".