Here's my vote in my not so humble opinion:
I am a bargain traveler ... there, I said it.
I use Priceline extensively and as a result, have a huge bias towards hotels that give stay credit and points for Priceline stays. Hilton is so arrogant that you only get points and stay credit if you book on
their site at
their rate. That means if you book on Travelocity, no points, no stay credit. If you book on Expedia, no points and no stay credit.
My first choice is Hyatt, but that's because where I travel, there are plenty of Hyatts. My second choice is the Marriott chain, because there are so many properties.
About the only reason I have any kind of travel with Hilton is that several of the programs that I participate in (mypoints.com, erewards) allow me to accumulate points in Hilton HHonors.
If I were traveling as infrequently as you do, I'd go for Hyatt ... with 4 stays you make Platinum and get at least some credit and privileges for your stay (like upgrades

). I like how I was treated from the start as a Hyatt Platinum member much better than I was treated as a Hilton Silver member (also requiring 4 stays).