Mr. Steinberger - What differences would be noticed at higher enlargements. Can a 40 year old lens really be noticeable better than a 15 year old lens?
No, a 40 year old lens won't be noticeable different then a 15 or 20 year old lens of another brand. In tests and at high enlargements, things such as barrel distortion, flare, ghosting, corner sharpness.... etc will begin to show. If large enough enlargement you will be able to tell a difference.
I have previously owned a Bronica SQ-A and three lenses. These lenses were the PS series of lenses, which are the newer (late 80's I beleive) of the Bronica SQ lenses. The 80 I owned was great. Very sharp. The 55 was a little soft. Very soft in the corners. All lenses are different. My 55 may have just been a lemon.
One of my MF cameras I now own is the Mamiya 6 and I have previously owned the Mamiya 7II. I have never seen lenses as sharp as the Mamiya rangefinder lenses. Granted I have never shot Hasselblad glass, but I have heard in tests and from others that the Mamiya lenses for their rangefinders are atleast as sharp, if not sharper then Hasselblad - Zeiss glass. The advantage to the rangefinder design is for the ideal placement of lens to film plane ratio which results in more sharpness.
I'm rambling here a little bit. Anyway, I'm sure your 40 year old Hasselblad lens can stand up to the more modern medium format SLR lenses of the day (excluding modern Hasselblad lenses). Take this into consideration when purchasing a new system.
I would agree that Hasselblad stuff is overpriced, but I think alot of it has to do with the collectability of it. You may sell your kit for something else which may not hold its value over time. Nothing in photography holds its resale value like Hasselblad and Leica.
But then again, we're not collectors, we're photographers!