What hotel award program is best for me?

I travel internationally about twice a year on vacation (Peru, Tanzania, Phillipines, Mexico).

I travel as part of my work too so I can rack up a ton of award points with the hotels my company puts me up in (that I can use towards my vacation accommodations). My work travel is mainly within the US.

I've been using hotels.com since they have so many different hotel brands I can book at all over the world. But hotels.com only gives you one free night for 10 nights. I wonder if there is a better program for me that still offers a lot of flexibility in terms of what hotel brand I stay at.

Thanks.