Let the hive mind of Engadget get that for you.
"I just switched to Sprint from Verizon about three months ago for the Pre. Then I went for the Hero about a week ago. Now, I miss my hardware keyboard and am thinking about switching to the Moment. I am still able to switch back to Verizon if I want and get the Droid when it arrives. Should I just trade up to the Moment when it comes out, see if I like it, and if not switch to the Droid? Or something else entirely? Help!"
I'd like to see the Moto Z come out on Helio instead of Verizon- it's already been made for Korea, it'll be easier to adapt it to Helio (a part-Korean company) than to adapt it to Verizon (All-American, and all-the-same styles... boring compared to Asia)