After a day of research skiing, I think I have my answer but still it's a tough choice.
Jim - l looked and the radius on my skis are 14m for the RX8 and 14.7 for the Magnum
Yesterdays conditions at Winterplace, WV - Very cold -8 F at the start of the day warming up to about 12F. So we had hard groomed conditions but nothing an east coast skier would call ice (if you couldn't skate on it, then it isn't ice), some patches of what I think people here call boilerplate ( chopped up stuff from grooming that is mashed down flat, very hard and irregular to look at but basically flat hard stuff)
I started with the SS Magnums. I was having fun even though my wax wasn't exactly right. I was beginning to think that these would be the ones. My son said, "You really rock on those skis." Why are you going to try your old skis? (My son, you'll understand these things when you are older!)
The RX 8 is just a very fun ski. (Note to our new dentist friend - these really are great skis and would be a great ski to advance skills on. They are not hard to ski, but at the same time, will perform for the better skier.)
These skis are very quick. I could notice in these conditions that the grip was superior, I would doubt that in Colorado for the camp it would make a difference. The narrower waist and edge to edge was slightly better. Doing one foot release and 2 foot release was easier. They have more rebound which I had to adjust to at first. The wax on these was better and they were faster. So fast that I noticed again that at the top end, perhaps because they are only 170cm, or that I don't usually get going as fast as they tempt me, I got just the beginning of nervousness. I have heard this before on other sites from big guys on the 170. It is nothing weird or squirrelly, just not as rock solid as my Head skis.(IM 75 at 170 and Magnum at 177).
This leads me to wonder if I should have gotten the RX8 in 175cm although I got mine here from Greg (thanks). It also makes me wonder about the original SS in 170 or 175. I definitely want to demo them when I am out at Solvista. It would be interesting to do a head to Head comparison with the RX8 170 and the SS 170.