Originally Posted by C17PSGR

There's two parts of the answer.

First, in Eastern Europe, South America, and Australia, there's not a lot of difference in the brand standard and in many cases, they aren't in the same countries.

I haven't stayed in Sheraton's in Western Europe or Asia, as the Marriott choices there are generally excellent.
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In the US, Marriott's are usually better than Sheraton's which are all over the place ranging from a dump to a perfectly acceptable business property. Having just spent a couple of days at a well-maintained Sheraton, one noticeable difference in the US is the lounge. The Marriott brand standard has the lounge open every S-Thursday night, that's not a Sheraton requirement. Also, the Marriott brand standard has a better breakfast standard than Sheraton (meat, not just eggs, more fruit and yogurt). The Sheraton standard doesn't seem much better than a Fairfield Inn, except for real plates and silverware. The evening snacks at the Sheraton lounge are also below the Marriott standard. I've probably stayed at 5-10 Sheraton's in the US and that's pretty consistent.

Bizarre though to split a building in Frankfurt between Sheraton and Marriott. Would be very interesting to understand the thought process.