I'm FO for the record and I've had the Chase Sapphire card for a few years now (not the preferred one, though they keep asking me to join up). I've done a ton of personal travel this year domestically, all using the Ultimate Rewards portal to book tickets for me and my fiance. I can tell you that if you put your FF# in when booking a ticket using the UR portal, it will link up your itinerary on DL and you'll get full MQM, even when using UR points to supplement the cost of the ticket.

The way it works is if you book the ticket on the UR portal for full-dollar cost, not using any UR points, Chase will book the ticket straight through to DL and you'll see a Delta entry on your statement. If you use UR points, you'll see an Ultimate Rewards Travel entry on your statement for the amount left in dollars, which should be the cost of the ticket less the # of points you used. Either way you book, you get full MQM's and the ticket is booked into a revenue fare class. I've found the UR search tool to almost always match DL.com and other fare search engines.

I've been using UR points to supplement some high-cost tickets for summer travel and have been getting MQM's and the every-so-often upgrade all year. The only hitch is that if you're traveling alone, DL will automatically list you as "Upgrade Requested", but if you book a non-medallion companion on the same ticket (which I typically do so she can take advantage of the medallion baggage allowance), then DL.com will list you as Upgrade Eligible and you'll need to call them to officially request the upgrade. Not a big deal, just something to be aware of.

I've been extremely happy with UR rewards (in fact, I refuse to get a SkyMiles Amex card since I've been so satisfied), especially since all tickets booked through the UR portal earn double reward points. I think you'll like the card, let me know if you think the "preferred" card is worth it!