Well, not to belabor things TOO much, but--
1.) Trumpeter already has an excellent Prime Mover version on the market, one I would purchase and build on a regular basis. DML's has been promised for nearly a year; Dragon USA is taking "Back Orders" on their web site. Trumpeter even has a "late" variant of the Prime Mover whose angled rear fenders will work well with later 7/1 and 7/2 variants.
2.) Trumpeter now have the flat bed for adding either FLAK gun for the 7/1 and 7/2 variant (a specialized gun mount on early versions was abandoned and the guns later on were simply bolted to the bed). The whole family of Sd.Kfz.7s is now wide open to them.
3.) They have the quad gun finished and presumably the 37mm in development? The 7/2 carried three different versions of the gun, so which one they pick will be interesting, and will there be options to build all three?
4.) They have an ammunition trailer (actually any small Wehrmacht trailer will work, I've seen variants). Greater value for money if Dragon's does not, presuming both kits sell for about the same $$$$.
5.) They presumably have the armored cab and radiator shield on the drawing board, if not in molds. The cab doesn't look to be anything complex or hard to adapt from their existing sprues based on the photos in The Sd.Kfz.7 In Detail.
6.) It looks as though Trumpeter has reduced the amount of PE that's in the Prime Mover kit, including winch detailing, turn signal arms, etc. While not onerous in the PM kit, I realize some modellers don't want the hassle of PE. Conversely, they have increased the PE factor over DML's announced 7/1, mostly in the gun shield, sight, and detailing.
7.) DML promises to render the gun shield in scale styrene thickness. I assume they wouldn't claim that unless they can do it, but we won't know until one of us has the kit in our hands. This seems to be in line with their recently-released kits that have less PE than their so-called "Premium" kits in the past. Most modelers seem to prefer OOB kits, so that would be an edge for DML.
8.) The final question for me is: has DML corrected some of the mudguard innaccuracies others have pointed out on the Trumpeter kit?