Hoss,
what has been said about the scimitar is correct. It is supposed to give better take-off and climb performance and also reduced noise, at a cost of 3-5kts in the cruise.
It has, however been my experience that when that sweet continental IO-520 is punching out 300 gee gees a decibell here or there is not noticeable. I am also of the opinion that it's climb performance is not as good as the McCauley and that the speed reduction is 5kts+ ..... not that I have any biases
VneII
PS. Milehighsociety, has the speed increase in UPN been scince it was fitted with a McCauley? She's a good bus that one
Also from what I'm told McCauley props are about $2000 more than Scimitar, can anyone comfirm?