Serge's post sent me looking around... After digging around the FAQs here - it seems that group and convention nights may not earn points as part of this, which would be a real surprise for me:

https://www.marriott.com/marriott-br...ection/faqs.mi

I see nothing about Concur, which suggests to me Concur stays would remain "qualifying stays" (likely as a preferred Marriott travel agent) but if it is indeed true that group and convention rates don't earn points, that would negate a good amount of the benefit of the program for MGM elites. However, I would note that the Marriott terms themselves are broadly murky in terms of whether convention rates earn elite nights - but they almost always do in my experience. Something that needs to be confirmed with Marriott...

I have a trip to Vegas in May myself for a convention - I could either book Park MGM via the conference site or book something like Four Seasons via Concur...