It all depends on what you are looking for and how you are earning your miles. For transferring to airlines, SPG is the only way to go. However, if you earn most of your miles from churning or CC spend, then HHonors may be the way to go. You can churn a Citi HHonors card a couple of times a year (plus use the 2 browser trick), which will give you about 200K per year plus spend. If you have the AMEX HHonors card, you can earn up to 6 points per dollar in various categories.

For SPG, you need to wait at least 12 months from the date of closure to get a new card. Plus the sign up bonus is only 25-30K at best.

So even tho the redemption levels are much higher, the earning RATE and potential is also much higher. With HHonors you also have the VIP and AXON redemptions that drop the "top" tier (excluding WA) to about 36K per night which is about double the SPG redemption for a similar type room.

Again, they both have their place and it all depends on your goals.