The JW is in a much better location with the Galleria within walking distance and a very central location if you want to head anywhere. Just about every restaurant known to mankind would be close by as well.

Not much happens in downtown in the evenings and on the weekends. Getting to downtown from the JW is not a hassle at all and if it is on a Saturday/Sunday traffic is not an issue.

If it was me I would do the JW hands down. Lived in Houston for 25+ years and all my family still lives there in case you were wondering about my knowledge of the area.