Hi Alessandro,
I thought I'd pipe up, there's already a bit of information here, but thought I'd throw in my experience with both system.
Firstly, I own an IQ160 and 645DF. I shoot fairly frequently with it, along with a 5D3 and recently an A7r, but have also used the H3D something or other, H4D50 and H5D50 as a friend uses their system.
As far as digital backs go, I would definitely rank the Phase One there, if you're looking at the IQ that is. I'm talking of overall use. It's a pleasure to use in the field when you can't shoot tethered. Tethered shooting is pretty acceptable too, but has the same limitations. I've found my back to freeze frequently and "apparently" is a fairly normal issue to run into on occasion.
The other thing I found shooting tethered was to run into issues with the buffer, but that's more because it shoots faster than the Hass. Generally not an issue though.
I think the new SK lenses are a little hit and miss to be honest.
The 80mm is solid, and works very well with a reasonable result. I don't like the 150mm at all. It's images are a little soft, and frankly the look it gives is not great.
The 110mm lens though, is my favourite lens, bar none, on any system I've used. I can't put my finger on it particularly... just overall it's the most pleasing photographic lens I've used, even a terrible photo looks great with it (this is purely objective though).
Because the relatively small level of focal length difference between the 80 and 110mm, I'll often use the 110mm in place, and step back a little.
But that said, I've had similar issues with Hasselblad lenses too on the H system. Some are hit and miss, though I haven't had enough time with the lengths to determine which one I like or dislike.
As far as bodies go, I prefer the Hasselblad body itself, its only downfall is it doesn't have a focal plane shutter, and thereby limited to the leaf shutter speed (I think it's 1/650th or somewhere around there). This is good for many situations, but can lead to compromise in other situations, which I don't like.
God knows when Phase One is going to release a new body that isn't related to the Mamiya goliath.
As you've already acknowledged, it's better to trial both, and see how it goes.