If you can only reach the Gold level in either program, I would shoot for HH Gold.

All discussions of devaluation aside, HH Gold is a superior status to SPG Gold.

If you had a legitimate shot at the Diamond/Platinum tiers, I'd probably flip this around and recommend SPG Platinum. Even with the numerous new (2012) subtiers within Platinum, the base Platinum status has always been a pretty good experience for me. Lots of full suite upgrades.

Or you could try a diversification approach: stay at one, everyday credit card spend with the other. I did this throughout my heavy Marriott years (used the SPG and HH Amexes) to keep meaningful balances and at least a basic elite status in all three of the big programs.