Although you know the difference, people who dont know anything about bikes (even some other riders) will think the fz6 is a rocket. Im consistently telling people i dont ride a crotch rocket. Ive never ridden a klr so couldnt compare the 2 for you. I can say the fz6 is a very practical bike though.
The beauty of it is, even though it's not a crotch rocket, it's every bit as fast (almost) as one so it's like a wolf in sheep's clothing that way.
OP, you asked this question on an enthusiast site for the Fz6. Do you really expect people to say it isn't a good bike?
In all seriousness though. I can't speak to the adventure aspect of it. However, as my 2nd bike coming from a 800cc cruiser, the Fz6 blows it away in terms of just about everything. Speed obviously, comfort surprisingly, cheap to insure, easy to maintain, reliable, fun, easy going in the lower rev range, and can become a beast when pushed. According to specs, my bike is pushing out about 95-98hp and weighs in at about 425lbs dry. My 800cc cruiser weighed in at about 500lbs and was only putting out about 50hp! The throttle (at least on my bike) is pretty linear and there's nothing scary about it at all. It's a smooth as can be and is a great, easy to ride bike for commuting and putting around. It can and does however, have an alternate personality when you get those revs above about 8K and I imagine, would keep up with most super sports save the liter bikes.
Whatever you end up deciding to do, based on what I've read, the Fz6R is a downgrade from the Fz6 so you would need to look at 2009 and below.
Good luck and welcome to the forums! There are a great bunch of helpful guys on here and as far as I can tell, no trolls at all (which is a rarity).