I am coming up on my 4th season as an instructor in Tahoe. In terms of personal stats: 5'11" and 155-165lbs.
I think, first and foremost, the two most important criteria when choosing a ski to instruct on are: comfort and confidence. You need to feel extremely comfortable on the ski and you also need to feel extremely confident on it. Additionally, it need to inspire confidence in you when you ski on it. Honestly, it doesn't matter what type of ski it is, as long as you are comfortable and confident whilst skiing it in a wide array of conditions and terrain.
That said, here's what I have used over the past several seasons:
The first year I taught on a pair of 188cm Lib-Tech NAS (99mm in the waist) and a 19m radius. They were pretty long and unwieldy when teaching on the Magic Carpet, that's all I can say.
For my second year I taught on a pair of 180cm Blizzard Titan 9 (86mm) with a 20m radius and they were a joy. While still a little too long when teaching the ruggers on the Magic Carpet, they were extremely versatile everywhere else (during my second season I was teaching more intermediates and advanced skiers, so having a more versatile ski was key). Perhaps the best thing about these skis is that I was not only comfortable skiing them all over the mountain, but they instilled a great level of confidence in me, as well. I never doubted their performance or how I would perform on them.
This past season I skied exclusively on a pair of 174cm Blizzard Magnum 8.7 with an 18.7m radius. This ski kicks a$$. It was great all over the mountain, from teaching beginners on the bunny slope to intermediates on the groomers and more advanced patrons in the trees, bumps, and powder. I found it to be very versatile and it was the only ski in my quiver for the whole season. I used it to teach, train, freeride, and take exams on. If you wanted something a little more piste directed, look at the Blizzard 8.1, narrower in the waist a bit and with a little shorter radius. I absolutely love these skis. I didn't think I'd be able to find a pair to replace the Titan 9's, but these totally did. I was comfortable and confident on them and this showed in my skiing, both in teaching lessons and in training (the feedback I got from fellow instructors and trainers).
So, I suggest that you pick a ski that you will be comfortable and confident on (stick with a brand you already know and trust or demo a few models that seem like they would fit the bill).
Edited by dookey67 - 8/12/12 at 10:00am