Gents,
It is not mere about the pixels and size of sensors. There are different generations of sensors and with them different generation technology and implementation. Those have led to improvements in image quality. Or Yair, please correct if there are image quality improvements between Credo and Aptus-II/AFi-II backs, and specific what such for different sensors?
Newest: 80MP Leaf & P1
Second: 40 & 56 MP Leaf, 40 & 60MP P1
(Steve left out the 40MP 44x33mm Leaf, the Credo 60MP assumably is same sensor as P1?)
Third: 28 & 33 MP Leaf, 30 & 39 MP P1
Fourth: 20 MP Leaf & P1
Sorry, no idea of Hassy. All Leaf are Dalsa sensors. P1 sensors are Dalsa from 40MP and up.
Personally I much prefer character from Dalsa sensors. My prior 28MP Aptus was identical sensor as the 33MP but a smaller crop.
Stepping up from the 28MP to the 80MP Leaf AFi-II last year, neglecting the more pixels I have found there was a significant step up in image quality. There are better colors, more colors, finer gradation of colors and I can push the files much more. Frankly it made me finally drop Velvia 50 slide film which I for landscapes had shot side by side at times for the appealing colors. The 80MP does not give Velvia colors, but bring per my critical eye indeed very pleasing colors (considerably more so and better than the 28MP). There is also less noise with the 80MP. And yes, the more pixels help in all these, including that I can crop and do so frequent. It does require more careful technique to get sharp images because many pixels.
I looked at sample files also from the 56MP Leaf and 60MP P1+, and found the 56MP Leaf to be a very minor step up in image quality compared to my 28MP Leaf, but the 60MP to be around halfway up in image quality to my 80MP Leaf. Though difficult to say precise how much up for the 60MP, they too are very good sensors indeed though not to level of 80MP backs.
I current use on Hy6 camera which is complete awesome and pleasure to use. That camera helps me to hand hold steady. If I used 80MP for Mamiya I am sure I would fail many more shots. One reason being that Hy6 has a waist level finder, thus I can cradle it to hold steady, as compared to lifting camera to eye level when standing. Also because camera is significantly more ergonomic, more balanced and much better quality with very precise focusing.
Regarding color casts, there is no difference if stitching within same image circle. If no stitch and need wides, with smaller size sensor arguably the SK 24 XL may prove more problem and lenses are more $$$ for similar width of field. You should look at specific lenses for the focal lengths you prefer.
Worthwhile to consider is also the Credo/IQ vs. Aptus-II/AFi-II/P1+ interface and price. Though I purchased my AFi-II prior the Credo backs were announced, the AFi-II offer a modern version back case of the Aptus-II and with rotating sensor and tilt screen. I find the AFi-II as very attractive also for a tech camera and plan on adding a tech camera eventually. The AFi-II is also considerably cheaper than Credo/IQ... and only tad more than Aptus-II. Prices vary in different regions, but the higher end Leaf backs in non Credo are well worth to look into as comparison to Credo and offerings from P1 and Hassy.
I am very very pleased with Leaf. Support from Yair is excellent. And from Gavin and his team in HK is truly superb! The solid product, service and support is what made me to spend the $$ to upgrade last year. Plus that the Leaf backs are durable to point I know I can trust.
Lastly, the rotating sensor from Leaf in the AFi-II backs is super. Prior using it I was concerned if due to the 80MP and the strict tolerances required for digital it really would measure up. It does. I get very sharp images both in landscape and portrait mode. Works excellent on my Hy6, and should work equally great on an Alpa. To my surprise I frank also frequent use and ejnoy the tilt screen on the AFi-II back. Should be great on a tech camera as well.
Sorry Yair, but doubtful if I will upgrade to a Credo. Love my AFi-II with Hy6 !!!
Hope above helps!
Best regards,
Anders