How and what are you going to shoot? The Mamiya 3 and 2 series are great cameras. Lens quality seems to be better with the later versions but even early seem fine. Multiple prime lenses so quality is not compromised. Minus of course is if walking around it gets to be a heavy kit and is not as unobtrusive as most of the fixed lens tlrs. I used to craze a C330f Professional system but as much of my photography is hand held walk around, it had weight against it.
The Yashica and Rollei models are lighter for walking around. But to get to a longer focal length or wider view when you can only do it via a different lens are the auxilary lenses. I've yet to find a set even the Rolleis that do not affect the quality. Yes, you can crop to get around the longer lens issue but in some instances can not get wider when your back is against the wall, no pun intended. Yes, there is the tele-Rollei but, last time I looked at pricing, I doubt you'd carry it around often.
I've had the Yashicamat-G and several Rolleiflexes, no 'Cords. On balance the Yashica is a good starting camera to test the waters with. It uses the Bay I filter set so if you later move up to a Rolleiflex 3.5, there is a good chance the accessories are transferrable. Do'nt get bogged down with the lens too much, the Tessar vs Planar debate, like trying to compare 2 perfects with each other. The 'flex lenses are simply for most part above almost anything you'll likely shoot. This tlr design is easy to carry and shoot with as they are vitually identical except for the Rolleiflex T. The Rolleiflexes I've had were quieter than the Yashicamat-G. If you look at Rolleiflex , look for a T. It is between the 'Flex and 'Cord supposively but in comparing it to both, it is really a 'Flex less the autostart mechanism so the same system as the 'Cord and Yashica, align the arrow on the film to a mark on the camera. It Does use the EV shutter system so the dual wheels are lacking. If you get it CLA'd the interconnect of the shutter and aperature levers can be defeated. I actually like the shutter button on the T better, I find less potential of body movement with less thinking about it. It also has the removeable hood for the 'Flex finders and is easier to replace the screen than the earlier non-removeable hood 'Flexes.
Assume that any camera you get should or will need a CLA to assure shutter speeds and lens alignments. The 'Mat-G and some Rolleis have some form of meter. Make sure they are either accurate or use it a bargaining chip. Repair and replacement of the selenium metering cells (Rollei) is not cheap, figure a trip to Quality Light Metric in California, the non-selenium meters I think all use the PX625 mercury so something like a C.H.R.S. adaptor will get you power.
The limiting factor result wise for each of these will be the user's ability; all are excellent cameras but, only a tool.