My two cents....
I get into Memphis a couple of times each year, most recently just this past weekend.
I stayed at the downtown Marriott a few years back just after it converted from having been a Sheraton. A number of issues during my stay, but I chalked it up to the fact that they were essentially in transition. I've not stayed at the Airport Marriott, although a gal I went to high school with has worked there for years and keeps asking me to give it a try.
Most recently, I've been staying at the CY in Southaven (just across the state line in Mississippi). Good property, but this past weekend I was staying on points and it wasn't available, so I went with the Fairfield up the street. Big mistake/multiple problems. I won't elaborate other than to say it wound up being one of my worst-ever experiences with a Marriott-branded hotel. That said, it could've been they were just having a bad night. Anyway, I like the area because it's just off the freeway with loads of restaurants, etc. nearby. There's also an RI next door.
I've also stayed recently in the Galleria area off I-40 east of town. Also loads of restaurants. A little more upscale selection than the ones in Southaven, plus a major shopping mall. There's a good SHS and Fairfield right next door to each other (within walking distance of a couple of restaurants).
I've also stayed at a couple of older properties closer in on the East side of town. A couple of Courtyards, a Fairfield, and an RI. No problems with any of them, but I wasn't particularly impressed, either.