So, a year on the "dark side" later:
2013 saw a total of 26 nights with Marriott, and 99 at a Hilton property. Enough time for a reasonable evaluation.
What do I miss? Points. Lots & lots of points. No doubt about it, Marriott Rewards gives me more points and things to do with them than Hilton. Keep in mind, what I do with my points may differ from you, but for my preferences (stuff from MR/SkyMall mostly), it's a better value. I haven't used many of the Hilton points as they accrue at a much lower rate, and merchandise (or nights) seem to be at a lower exchange rate overall. So from that particular perspective, I'll still remain loyal to The House That JW Built to keep that bank filled.
What don't I miss? The Bistro. That is the most McDonald's/Walmart concept I can think of where it relates to attracting regular clientele. If I'd only been to a single CY, I'd think it's a great idea, but after the 40th or 50th one, c'mon, man! If I sought a generic, unified corporate market-tested concept, there's always Olive Garden, Red Lobster, et al. I still like a wee bit of uniqueness. I don't miss the loss of Platinum Welcome gifts at full properties. Was the half-bottle of wine and bowl of nuts really breaking the bank? 500 points, gee, thanks. I don't miss Platinum Premier, either. It got nothing except an annual cheesy gift and a black card. As an LPE, I get the same benefits and treatment as I ever did with PP, so no great loss.
Now, Hilton isn't all that either. I've had properties that were as underwhelming as any in the Marriott family (I'm looking at you, Doubletree), a 30-year old Hampton in East Nowhere, Kansas is still a depressing crackerbox, but I've also had some really nice experiences. Embassy Suites is a terrific brand concept, HGI's are usually above average, and I can actually get a cup of coffee without shelling out $2.50. The Hampton in Lexington, VA is really something (a renovated 200+ year old home as the main house), some surprising on-property restaurants (a Ruth's Chris attached to an HGI? Yup). As a Hilton Diamond, I even get reserved parking spots at some of the properties. How cool is that?
I think the biggest difference between the two majors shows up in the budget and mid-range properties. Marriott has a more consistent presentation, while Hilton tends to more variations within a brand. I prefer the variety, personally. At this point, I don't see a reason to move back to Marriott as a full-time provider, but I'm never going to abandon it entirely, either. I'll still make sure I get my 25 or so per year (or at least as long as Megabonus hangs around), and in some locales, Marriott has a better selection (Manhattan, for example), or may be the only one there (Victoria, BC).
So there you have it. I'm coming out as bi (-hotel). I still have 20-30 Marriott nights this year pending (plus burning 120K at the Marriott New Orleans in June for a REAL VACATION!), but I think that for whatever time I have remaining on the road it'll be predominately Hilton (at least until they irritate me beyond redemption).
Now if there was only a Hilton HHonors® Insiders...