The original Snuffers, back in the day, were designed as a 1 1/2 inch cutting diameter (the largest size Magnus makes is still close to this) based upon testing during the time Dad was developing them. He was hand building the heads back then (this would have been like the late 1960's) and made sizes from 1 inch to 2 inch diameter with several in between. The heads were used on deer with accurate records of recovery distances, blood trail etc. It turned out the 1 1/2 inch heads were the most efficient out of the sizes he made. For years and years that was the only size manufactured.
When the business was sold to Delta, later to Magnus, the different sized heads were made to fulfill the market demand. Frankly, to ME, a REAL Snuffer is the 1 1/2 inch head. I don't recommend using the heads smaller than the 145 gr size due to the amount of metal taken off to reach the smaller sizes.
As far as the Woodsman goes - that head was marketed as a "3 to 1 ratio" 3-blade head in the beginning. The idea is enhanced penetration. Good for lighter weight bows, etc. Both manufactured by the same folks now, so the quality should be comparable.
If your "pro staff" guy told you development of the head size had anything to do with accuracy at long range he needs to go back to "pro school"
Ryan