I would buy whichever is lower priced as I will not pay extra to have another name stamped on the same product.As far as scopes are concerned ,I would go with the 40mm lens as the 50 is not required and you must mount it higher which makes it harder to obtain proper cheek positioning on the stock.As far as ammunition is concerned you can use any ammunition designated 7mm rem mag in a 7mm remmag rifle reguardless of the manufacturer.