When I was primarily Marriott, Hilton was my back-up chain. Reasons being that they had a lot of properties worldwide & a lot of brands at different price points (which was one of the main reasons I was Marriott).
I thought of going w/ IHG once I blew through all my Hilton points & had switched primarily to Marriott, but given their lack of bennies, if I was going outside of MAR/SPG I'd go w/ Hilton.
* SPG is now my 'back-up' chain given the merger. In the past I would have chosen Hilton over SPG.
Cheers.