I made Hilton Diamond earlier this year, and I'm now going for Marriott Gold, specifically because I've heard that reward redemption is a lot better.
I may go back to Hilton next year, though. Reason being that even though reward redemption might be better, the experience of staying in Marriott properties has been pretty miserable so far. I disagree with everyone who says that Marriott is more consistent. Perhaps at the high end, it's better, but I usually stay in the lower end properties (Fairfield, Courtyard, SpringHill at Marriott and Hampton/Hilton Garden Inn at Hilton). In 10 Marriott stays, I've had one time when I had to move rooms because wireless Internet didn't work at all in my original room, another two times when the wireless access was so flaky that it was barely usable, another time when I came back to my hotel to discover it surrounded by police vehicles and police tape, another where MR did not credit my account properly for the nights I stayed despite multiple faxes (and with no phone call or other communication to explain why), etc., etc. I'm starting to actively avoid Fairfields because I figure I could book Motel 6 for similar quality at half the price. On the other hand, in 30 Hilton stays, I can count on one hand the number of problems I had. HGIs are consistently excellent, and Hamptons consistently range from acceptable to very good.
I figure why should I have to endure substandard accomodations for 50-100 nights a year, just so I can have four wonderful nights on vacation, if there's even availability? I'd rather pay for the vacation nights and be happier during my day-to-day business travel.
As always, YMMV. I go to different locations all the time, so consistency is really important to me. If you are always staying in high-end properties, or only going to one or two spots where you can find the best Marriott property around, then yes, I would suggest Marriott, due to the better reward redemption.