Steigenberger is 5* and about 160€/night (single), Windsor is 4* and 80€/night (single). You are correct concerning location. Windsor is just next to S-Bahn (suburban transit) rail station Düsseldorf-Werhahn, about 2 minutes to walk.

Walking distance from Windsor to old town (claims to be the largest pub in the world) is about a mile, same distance to the Königsallee. Local public transportation (tram) is frequently running until late night. Steigenberger would be right on the spot.

Next to Steigenberger there is a huge subway construction site.

If budget is an issue, go for the Windsor.

Enjoy your time here