Demo them both
. I've heard alot of good about them both. Love my new Villian too. There are several kayak shops with rentals or free demos in the Portland area, and lots of used boats too. At Alder Creek, you could probably take these boats out in the bay 100 feet from the shop, and answer 1, 2, 4, and 5 for yourself in an hour.
I haven't paddled a Karnali, but I don't think there will be huge differences between those boats. They are both considered to be fast, easy rolling, stable.. Beginners would flip more in playboats, and those will be somewhat harder to roll too.
Beginner/intermediates should practice their roll and brace every time they go out, and get good instruction if they need it. I see too many intermediates without a solid (and fast) combat roll. That is way more important than what boat they are in. A poor combat roll will lead to a scary swim sooner or later; then many tend to quit the sport, which is a shame.