I've flown the Nexstar a couple of times, and my first trainer was a Kadet MkII. I think the Nexstar is a great plane, very stable, and slower in pitch response than the Kadet MkII. The Kadet has a shorter tail moment than the Nexstar, makes it a little "twitchier" in pitch, a bit quicker in rudder response. I built my Kadet with about half the stock dihedral, so it's hard to say how the roll responses compare, but I imagine the stock Kadet is probably a tad more resistant to roll than the Nexstar, and would tend to stabilize better in straight and level flight.

I really liked my Kadet, I thought it was pretty easy to learn on. Unfortunately, I found out the hard way that it doesn't do well in midair collisions with 1/4 scale planes. I bought my nephew's Superstar after that, it's even easier to fly, but not as capable (IMO) or as much fun.