Lisa,
Do you have the opportunity to rent these different systems and try them out? Or access to different sales reps that would let you demo them? The reason I ask is that I get the sense that you want to fully research your different options. I'm right there with you! As a DL28 user, I can provide my own experiences but my hunch is that if you're anything like me, you won't be happy until you've played with the different systems and decided what feels right.
Back when I owned a Mamiya ZD back, I bought it sight unseen. I used it with my Mamiya AFD camera body which I had owned for a while and knew well. So, while I was aware of the pluses and minuses of the AFD, the ZD was new territory for me. After a number of issues (well discussed on these boards), I decided to try out a few different systems. I didn't play with the Hasselblad (because I already had Mamiya lenses that I didn't want to get rid of and buy into the more expensive H lenses). But I did test a Phase back as well as a Leaf. Ultimately, I liked both but just 'felt' better with the Leaf. Combined with a good deal, that's what I went for.
In your case, since you're considering multiple systems, I can only suggest that you get some solid shooting time with the different systems (be it Mamiya, Phase, Hasselblad H, H2, H3, Leaf, etc) and make a pro/con chart for yourself.
Ultimately, I think it's the only way to go about a purchase (and potentially dealer relationship) of this magnitude.
Good luck,
Josh