Well, Denver's RTD is far from choosing a design. They in fact are allowing all the companies to "bid" for their business.
RTD's request is simply an FRA-compliant EMU, BUT they need the winning manufacturer to produce a DMU-version
of that identical EMU train and be granted FRA-compliance.
The GE/Budd style, Arrow VI's DDMU's being pursued by the NJ Transit are simply for forerunner at this time, to having a product which meets
Denver's requirements. However, RTD has a close working relationship with Siemen's. RTD-Denver is Seimen's largest LRT customer in the nation
at this time. Denver has ordered I believe 104 SD-60 model LRT's in the last 10 years or so and is expected to be ordering even more.
A Siemens EMU would be perfect for Denver's RTD, but Siemens will have to obtain FRA-Compliance for a DMU version of it,
in order to win the contract.
This is the most likely model to win Denver's contract after the Arrow type shown above...
With the huge contracts Denver has given all to Siemens for their LRT's in recent years, Seimens may be willing to expend
the funds to win this contract for over 100 EMU/DMU FRA-compliant cars (which would probably look like this):
So come on Siemens, you are Denver's best hope for a modern commuter rail train!