Has CMOS sensors reached image the quality of the CCD sensor?
This is too vague a question to be answered meaningfully. There are at least four medium format CCD sensors and three medium format CMOS sensors that are relevant to this conversation.
In general CMOS reduced noise and increased dynamic range. These are pretty objective and pretty indisputable.
Tonality and color are more subjective and vary as much within the "CMOS" and "CCD" groupings as they do between those groupings. For example I find the difference between an IQ2 50mp and IQ3 100mp Trichromatic larger than the difference between an IQ1 40mp and IQ1 50mp. Color and tonality are more subjective, so I'd refer you again to our database of raw files, or your own testing.
I'm pretty biased, but in my personal experience the best color is on the
trichromatic or IQ4 150 coupled with Capture One.
Does 50mp cropped vs 60mp full frame make that much difference in image quality?
The difference between cropped medium format and full-frame 645 is very roughly the same as the difference between small format and full-frame 645.
The crop means that lenses are effectively longer, depth of field for any given aperture is a bit deeper, and the viewfinder is a bit less spacious to compose through. Whether this makes a small or big difference to you depends mostly on you. For example, if you find yourself shooting wide open with any regularity then the shallow DOF that full frame 645 allows is pretty hard to pass up, whereas if you only ever shoot in the middle of the aperture range then that specific difference is moot. If you're coming from small format the viewfinder will feel larger and more spacious to compose through, even if you only go to crop medium format.
For environmental photography with ambient light mixed possible with CCD without resorting to long exposures?
The key question here is what is the highest ISO you find comfortable image-quality wise. Best to do your own testing to know for sure, but if that's not possible or practical, then we (DT) have a large database of raw files, including ISO sweeps with various backs. If you do your own research make sure it's opinions/files formed with more recent versions of Capture One. For example, when the IQ160 launched I was thoroughly unimpressed with ISO 200 (full resolution), but by the time Capture One had been updated several times I found that even ISO 400 (full resolution) was pretty decent in most situations.
Is the newer bodies that much better for focusing and recomposing?
They can be, yes.
Both the XF and H4 and later have modes for focus-and-recomposing (AFr for the XF and TrueFocus for the H series). When shooting with shallow depth of field and large recompositions these modes can be quite helpful. Though I'd note that people shot medium format for many many years without any such modes
.
Note that the XF is on it's second generation AF sensor (HAP-2) and has had several firmware revisions to improve it's autofocus. Keep this in mind when you read reviews from early in its release when the AF was not as confident, fast, or precise.
I know that CCD uses a lot of power, had they improved the power consumption over the years?
Not really.
If you are tethering, depending on the model of back, the back can receive power from the tether cable. If you're not tethered (or tethered by a means that doesn't provide power) then expect to run through a few batteries during a long day of shooting.
The XF and IQ share the same battery type, and
phase one batteries are only $70.
Is the waist finder that much better on one system?
The WLF on the XF is collapsable and you can use both autofocus and metering.
Is the view finder better on one system?
The Hassy viewfinder is lighter and more magnified.
The XF viewfinder is a bit more neutral and a bit brighter.
I find them equally sharp, or slightly favoring the XF in sharpness.
Coming from small format either viewfinder is going to blow you away in every way.