I’m a Marriott and IHG guy and have been for 2 years now after primarily being Marriott for 15 years. I mainly travel in Asia so I can’t speak to Europe or the USA but I’d say IHG offers a better value here once you get the 40 nights that unlocks the lounge pass. Some Holiday Inns and Crowne Plazas have lounges and they are usually decent and all Intercons seem to have them as well. There are great and reasonably priced Intercontinentals and even Regents in Asia that are much better value than the Marriott high end brands in Asia.
Marriott has taken a decision to drive up their prices worldwide it seems and IHG hasn’t done it so dramatically. For that reason alone, it’s worth a look.