Geography. It's a big place. I liked the latitude point and the sun/darkness balance. I'm in Grand Rapids, MI and while that's north in the US, it's actually a tad south of Bavaria's latitude. I've considered growing hops here and lots of folks are. It's quite the growing industry and I've met several folks at beer fests and even bars (Founders) that are marketing their hops. The weather is a bit milder here on the west side of the state as Lake Michigan is a pretty big heat sink; lots of fruit orchards here.
Anyway, it seems to be a good hop growing region, but my particular neighborhood is nothing but huge old growth oak trees. Tons and tons of shade. Hard to even grow grass...lot's of moss, though. My understanding is the hops need tons of sunlight during the summer. That's just not my yard...unless I try to grow containers on the roof!