Although you say location isn't really an issue, St. Louis isn't small, and you might want to give some consideration to what you'll be doing over the weekend. Sightseeing? Restaurants? Shopping? Vegging by the pool?

The Ritz-Carlton in Clayton is at the top of the Marriott properties, and there are a number of very good restaurants close by; Forest Park (Art Museum and Zoo, etc.) are also convenient, and it's probably the easiest drive to the Central West End, my favorite part of the city (I grew up there, which may have something to do with that).

The downtown hotel in my memory (it's been quite a while) is a fairly ordinary Marriott, but being downtown could be fun. The airport Marriott is also pretty standard issue - very funky 60's design outside (and the pool is not too good). The Concierge Lounge is good for plane watching, as is the bar on the top. The Lounge doesn't serve on the weekends, (and they'd crammed about sixty dozen tables in the last time we were there, NOT an improvement) but it at least used to be open if you wanted to go in and sit. I don't know what the situation is since 9/11.

Both these hotels are quite large, and often have large groups in - be warned about that. The Pavilion (downtown) will have a parking charge. The airport didn't, except for valet, but again, things may have changed.

There's also the Marriott West out at Westport Plaza (shopping mall) but we've never stayed there. It has always seemed pricier than the other Marriotts for weekend stays anyway.

Have fun.