I own a Yashica Mat 124 (not "G", so the "previous to the last" version) and I really like that camera: smooth, silent, ... Is the Rolleflex so much better that I should have a look for one (never had one in my hands) ?
Stefan.
I have a Yashica 24 and a Rolleiflex 2.8E. They are both fine TLR cameras. The engineering, craftsmanship, and materials that went into the construction of the Rolleiflex are significantly superior to those of the Yashica, though. It is easy to tell the Yashica is a lower-cost copy of the Rollei.
Some differences between the two cameras:
The foam light seals on my Yashica have degraded around the door and between the hood and the nameplate. The Rolleiflex does not use foam or fiber light seals; the door forms light traps when closed.
The Rolleiflex automatically sets the film for frame 1, whereas the Yashica requires lining up the arrows on the film with arrows on the the camera body. This is not really a big deal, but is a difference between the two.
The door on the Rolleiflex is easily removeable, but is not on the Yashica.
The hinge for the door is held in place on either side by metal plates on both cameras. The metal is much thicker on the Rolleiflex. It appears to be just stamped metal on the Yashica, and not nearly as sturdy. One of the plates is bent on my Yashica.
In the chamber between the taking lens and the film, the Rolleiflex has baffles and a black, light absorbing rough-textured surface. The Yashica chamber is painted black with what appears to be low-gloss paint, and part of the chamber is angled such that it can reflect light back onto the film. That somewhat reflective chamber surface in the Yashica causes flare when a bright light is in or near the edge of the frame. Putting a black flocking on the Yashica's chamber walls helps get rid of the flare, according to before-and-after pictures I've seen on flickr.
Mounting the Rolleiflex on a tripod is much easier, and more secure, when using a Rolleifix attachment. The Yashica has no provision for such an attachment.
The Rolleiflex 2.8E has a lock that ties the Shutter Speed and Aperture adjustment knobs together, so that it is easy to keep a constant Exposure Value while adjusting either. The lock can be unlocked. The Yashica 24 does not have this feature. Also, the Rolleiflex has an Exposure Value indicator, which the Yashica does not.
The Depth-of-Field indicator on the 2.8E is out of this world. It is my favorite feature on the camera. I won't try to describe it in words, but will just say that setting hyperfocal focus is as easy as pie with the way it works.
When using the Sportsfinder, the Rolleiflex has a mirror and lens that allows critical focusing on the ground glass. The Yashica does not have this feature.
The Yashica 24 takes 220 roll film, as well as 120. My Rolleiflex only takes 120.
The light meter for the Yashica requires a battery. The Rolleiflex meter does not.
The light meter on my Yashica no longer works. I had to have the meter adjustment knob fixed on the 2.8E, since it broke shortly after I acquired the camera, but now the meter appears to work fine.
The Yashica has a cold shoe, but the Rolleiflex doesn't.
The Yashica's focusing screen is superior to the original focusing screen that was on the Rolleiflex. I had Harry Fleenor put a Maxwell focusing screen on the 2.8E, and now they are roughly equivalent. I really like the red grid-lines on the Yashica's screen.
The major difference was what I paid for the cameras, though. The Rolleiflex cost much more than the Yashica, so I tend to be more comfortable using the Yashica (not worried as much about destroying its value).
There may be some other differences, but overall I really enjoy both cameras. If you've got a good copy of the Yashica, my recommendation is to keep it and take lots of pictures. It's a fine camera.