One minor point to add to BillMorrow post is that HH offer a VIP (silver and above) reward of 100K for 6 nights in certain premium hotels worldwide and Hawaii. There is also a offer that includes the air tickets, but I can't remember how many points you need - I think it is a bit more than the marriott however.

Milesrus. HH also has the United points for flying bonus, 4000 points for each four stays in a quarter, and various bonus airline miles deals at the moment, as well as the 2000usd spends bonus.

IMHO With the addition of all the extra Hilton properties, the changes to the earning ability i.e. any rate earns, and the double dipping, I think HH is hard to beat.

The last posts are an excellent idea. I would see which program fits your needs best, and then ring them at the end of the year and say 'if I move all my hotel stays to you, what will you give me?'. If you have some history with the program, you will probably be better received rather than phoning 'cold'.