I ran into both types of sales people. I've even had two different types from the same dealership. When we were looking for our 1st TT I really didn't know anything other than that my truck was rated for 6500lbs towing and 650lbs TW. At the same dealership I had one guy say I could tow the TT we were looking at, and not more than 5 mins latter one of the more experienced guys said no way.
Last year while looking at 5'er s at an RV show we were interested in several that fell into a certain weight range. When I told the sales guy what we were looking for he said "you driving a 3/4 ton?". We were.
Some just care more than others about customer relations than making a sale I guess.