Originally Posted by
Flying Lawyer
The regional express departing at -31 and -49 past every hour has four extra stops on its way (Deutz, Mülheim, Leverkusen Benrath) and that requires an extra 10 minutes. The fare is by far cheaper and these double decker trains give you good sights.
The fare (hbf to hbf) appears to be 9,80 for the RE, 11,00 for the IC/EC, and 16,50 for the ICE. If buying a single ticket and the next train was an IC or EC, I'd take that rather than wait around for the next RE.