Several issues here.

As some have pointed out, DL typically does not provide hotel for IROP due to WX. There are rumors that, as a PM or DM, you might get lucky. I have. My experience is that you will be more likely accommodated in DTW than ATL. Vestiges of the NWA focus on customer service, I suppose.

Now, your situation was due to a MX.

I have run into situations where I was assured, at the originating airport, that I would receive hotel accommodations when I got to ATL, only to be told upon reaching ATL that there were no rooms available.

Except in the most extreme weather situations "no rooms available" means that DL has given out all of the rooms that they have held at their negotiated rate. It does not mean that there are no good room left in the vicinity of the ATL airport.

Within about 5 minutes of being denied accommodations by DL, I had a reservation at a quite satisfactory Hampton within a few minutes of the airport.

I put the room on my credit card, then contacted DL customer service and sought reimbursement.

It took a while, but I finally received a check for the full amount.

Don't let them foist a heavily-restricted e-voucher onto you. As DL management intends, you'll just have to spend more of your money on a plane ticket in order to claim the value of the voucher, and you'll only have one year to do so. Insist on compensation of the form you used to pay for the room... genuine coin of the realm.

The advantage of paying and seeking reimbursement is that, if you are in a hotel travel program, you will get credit for the stay. Generally, if DL is paying directly, you will not get credit.

(Although, I was once able to get credit on a DL-paid stay by charging something to my room... a $5 purchase from the hotel sundry shop.)