Marginal difference really, especially given the FRA Sheraton looks quite a bit like the new brand of Marriott. You'll see some trends here and there and over time each brand had their own attributes (Sheraton had/ has a terrible Link Cafe in its middle aged branches), but generally they're two different sorts of out-dated poorly designed American style mid-level hotel. Both have lounges (the Sheraton FRA's lounge is/ was quite good).