At first I thought milesus suggestion was poor because you would miss getting the best tier you could get since the nights would be split between several programs. But maybe not.

Since there are only six months left in the year and I believe every elite hotel program operates on a calender year schedule, you might not make a beneficial level of status with any program, depending on your travel plans. So if you're not going to reach at least mid tier (where IMO you begin to get actual benefits) you could cross your nights between the three big programs and see which hotels you feel are in general are nice.

Marriott is my personal choice because they have a huge number of locations spread everywhere, and things are generally extremely consistent. But the new Silver (formerly gold) tier of their program has given me nothing.