As teachers we should be comfortable with both. I use the CX2 for flight planning and study questions, but in the air I think I prefer the whiz wheel because it is faster and more impervious to bouncing, missed keystrokes and battery failure. Generally one is not as worried about accuracy in the air as in planning or testing, and of course the mechanical wheels are not quite as accurate. In real life neither is used for vfr flying much anymore, so it's mainly educational.