Your body can convert Cyanocobalamin into Methylcobalamin and Methylcobalamin is prescription only so there should be no problem with what the doctor uses/prescribes (and you should not be messing with vitamins/minerals without your doctor's input as they can mess you and your other medicines up bad); it's like many other vitamins we take D2 versus D3, beta-carotene/Vitamin A, etc.

Vitamin B12 QuickFacts

One should only be taking Vitamin B12 if the doctor has done the blood work and you have a deficiency and s/he knows the cause; it cannot improve conditions if you do not have a B12 specific deficiency; it does not give athletes more energy, help with weight loss, etc.