You're comparing mostly correctly. But your math is off.
For gold you get 18 points per dollar spend, plus whatever the ongoing promotion is (right now, it's an extra 10 for everyone or 20 for amex hilton cardholders).
Running the numbers with 28 ppd on the spend and me estimating $1900 pre-tax on your provided numbers... it comes out to an estimate of somewhere around 5.7 cents per point value on the example stay you have given (with 53200 points + 280000 points == $1900). So, you are potentially saving around 10%, with the tradeoffs that you have noted. (non-refundability of points for $$ if you cancel your stay. Spending your points vs earning them and having them waiting for use later, etc.