I'm not up on all the DX systems, but the ones I'm familiar with were avoiding R-410 as it's want to stratify, concerned manufacturers about the long loop refrigerant/oil recovery.
Check all the things on the what to ask list, and if rebates/credits are guaranteed and installer checks out.....
My biggest concern with DX in the near term is that it is more attractive to geo newbies for a variety of reasons. Therefore I would suggest that no one purchase a brand no one has heard of from an installer that's new to geo.
In the case of DX such as Earthlinked and 1 or 2 others, the distributors are very active in the field which at least keeps the newbies out of trouble.
On the shoppers list, you may notice that brand/type is last (and by default not very important). The exception to that is when no one has heard of it or it is not certified for credits/rebates.
Good Luck,
Joe