All 3 of the Viking dealers in my area have the Diamond in - I'm surprised they aren't in where you're at. The differences between the Pfaff and Viking top of the line machines are getting fewer and fewer, although there are still some (Viking's Sensor System vs Pfaff's IDT comes to mind.) The embroidery fields, hoops, software, etc. are too similar for me to even use them as meaningful measures. They both have the design positioning now, which I thought was a pretty nifty Pfaff feature, and both screens are sharp with good resolution. Both have had update features for a long time; even my older D1 has been updated in the last year.
Most, if not all of the top manufacturers are coming out with new TOL machines this year - I've decided to wait and see what else is on the horizon. Babylock and Janome have both come out with their versions of the integrated dual feed; I'm waiting to see if it is on the Babylock TOL.
My can't live without feature has got to be the sensor system; I am used to the automatic presser foot, the pivot feature and a foot tap to control my needle all leaving my hands free to control my fabric. I haven't seen anything in the new TOL's that have made me want to rush right out and spend that much; if the other brands that come out this year leave me feeling the same way, I'd rather scoop up a couple more Designer 1's.