Reading on the HHonors Double Dip page, it looks like a stay a the Hilton Garden Inn can earn you the 500 miles in addition to the 10 points per dollar, is that right? Only the Hampton brand is excluded (or rather earns you only 100 miles)?

I am asking because the two hotels are basically in the same price range in the town where I am looking to stay.

If that is the case a one-night stay at the $89 I will get:
1,023 points (890 + 15% due to Silver status)
534 points because I will pay with HHonors AmEx
500 miles

That is not that bad in relation to the spend