I don't know much about Marriott/SPG or Hyatt. But I'm quite satisfied with Hhonors. The complaint I hear is that Diamond status is being watered down... more crowded lounges, less upgrades, less late check-out, etc. But I still love it, because you accumulate points fast, you get free breakfast (most of the ones I stay at give full breakfast, not continental), and EL's are typically still way better than your average United Club.

If you have a Hilton AMEx card and Diamond status, you will earn 30,000-40,000 pts (depending on what promotion is going on at the time) for every $1500 you spend. Based on my valuation (~0.55 cents/pt right now, I'd say), that's about $200. So you're earning back ~13 cents on every dollar you spend at Hilton.

If you have Chase United card, you'll earn ~25,000 UA miles for every $3500 you spend. Based on my valuation (~1.5 cents/mile, which may actually be higher than what most others would say), that's $350. So you're earning back only ~10 cents on every dollar you spend on UA.

And a further important consideration is that Hilton pts are far easier to redeem than UA miles at their respective appropriate values, not to mention the greater flexibility (point stays can be cancelled without penalty, etc).