Their service is more personalized. A small, seasonal operation. They have lots of local experience in the Vail Valley and on the Blue River. These guys will work hard to put you over fish. Large Operations run lots of guides.
Many guides are good to excellent.
Some can be good fishermen, but may be relatively inexperienced in this area. Check out the license plate on the vehicle that picks you up for your trip. If it's out of state, as many can be, you might be justified in having some concerns. This local Orvis shop has a wonderful retail operation year round. Probably the best and largest stable of guides in the area.