Personality Types play a huge role in how well a student-teacher relationship will unfold, and in turn how much the student will recall and hence learn at the end of a lesson. Uneasiness caused by an instructor can also narrow your perceptual field, and hamper your progress with learning what you really ought to know.

If you feel that one instructor is helping you to relax and be at ease more than an other, then I reckon that you've made the right choice by switching.

I have a feeling that this green CFI is just uptight because he hasn't had much experience. That can play a big part.