Just back from another stay at the Renaissance Brussels which I loved (until this weekend). This property is in line with many Renaissance Hotels (come on LHR get your rooms + exec lounge remodelled asap), and Brussels has some lovely rooms and suites as well as a good swimming pool and inexpensive weekend rates. However, they have now decided to close their executive lounge at weekends (as of 26th Aug just gone). In fairness, the hotel provides you with a voucher for free wine and beer plus 2 (tiny) plates of tapas at the public Schengen bar in the lobby and continental breakfast in the restaurant. However, the drinks are only available from 5.30pm - 7.30pm whereas the lounge was free and easy to visit whenever you wanted and the canapes and hot food was always very good, which again, you could help yourself to and have what you wanted. This change of policy has made me think twice about staying at the Renaissance again. The Brussels Marriott is currently being renovated and hopefully their rooms will be more upmarket than they were. On checking the Marriott webpage, they say their brand new (and must say lovely looking) exec lounge is open 7 days a week. I prefer the Renaissance but from now on it may have to be the Marriott.
In line with so many Marriotts in the US and Europe the closure of Executive Lounges on weekends continues to be a major reason I consider other hotels for my weekend stays. As you mention the Brussels Marriott is a good alternative, and always has the lounge open on weekends
I only stayed at the Brussels Renaissance once, and it was nice, but way out of the way unless you're going to EU meetings. I've stayed many times at the Brussels Marriott, which is right next to the Grand' Place, and have always been upgraded to a suite and treated wonderfully. Plus just on both sides of the hotel (near St. Catherine and also on the Grand' Place there are excellent restaurants.