I bought my first Bronica ETRS in about 1981, the lenses at that time were the MC series. I remember the first time I put a B&W negative from my first roll in the enlarger and used the 10x magnifier to focus. I was disappointed as the negatives seemed less sharp than those of my 1960s era Nikkor 105mm F2.5 lens (which was razor sharp). But as I made 11x14 and 16x20 prints, I came to appreciate the benefits of the larger negative. Sold the ETRS system during a divorce in the late 80s.
In the last 6 months I have purchased ETRS equipment from evilb@y, and do have the 50, 75, and 150 PE lenses. Subjectively I would say they are a bit sharper than the MC, but not worth the difference if I had to pay "new" prices. I still do not think they are as sharp as some of my old Nikkor lenses, but I still get great enlargements, I like the shallower Depth of Field (compared to 35mm) and am glad to be back in the darkroom again. I have also recently purchased some 6x9 "folders", like the Franka Rolfix with Schneider-Kreuznach Radionar lens, and though they are only around $50-75 evilb@y, the negatives are 2x larger than the Bronica's 6x4.5, and I love the 11x14 prints from the Rolfix, I think they rival prints from Bronica, though lens choices are non-existent. I like the soft edges when shot wide open, and stopped down to F8 or F11 images are sharp all over. Now I always keep a "folder" in my camera bag and take it wherever I go.