If you can book FHR within a few dollars of the MLife gold price, I'd go the FHR route.
Aside from the MLife Tier Discount itself, you don't give up any of your MLife Gold perks by booking some via some other method.
And I have found over the past 18 months that booking suites at MGM properties via MLife actually puts you at the bottom of the totem pole as far as getting your room preference when you arrive, unless you are a big player (which, if you're Gold, you're probably not, relatively speaking).
I've stopped booking suites at MGM properties via MLife because I got bumped out of them on 3 trips in a row.