I recently acquired a Mamiya m645 and after shooting with it a bit decided it may be overkill since I already have an RB67. the 645 doesn't do anything the 67 does just a bit smaller and can get a few more frames out of it with the 645 format. I know it's all objective but was curious what people thought as to whether or not to keep the 645 or go with another route. I love the RB67 and it works great with portraits which is what I will primarily use it for but have taken some nature photos as I don't mind handholding it. Any advice on picking a different medium format that does something the RB or 645 doesn't do or would I be wise to keep the 645. All opinions but curious to here people's experiences.