Unless you have to top out to get a particular reward, I would take a hard look at the conversion rate from HHonors points to any miles program. I would limit conversions to "orphan" miles inbound and even then I try to catch a special on the conversion rate (e.g., 4 for 1 rather than 2 for 1, or, apparently, the current one with Delta 2.5 for 1).
Also, look at the HHonors VIP awards (e.g., two tickets and a 6-day stay at participating hotels worldwide); it's competitive, but especially when you've recaptured value from orphan miles.