Starwood? Pffft.

PRG blows SPG away 7 ways from Sunday.

PRG gets 2x at gas/groceries, 3x on airfare. SPG gets 1x on all.

PRG has as high as 75K MR signup bonus. Max is 30K for SPG (once a year).

Amex gives MR transfer bonuses. SPG only has 25% in 20K increments to airlines.

There are multiple MR-earning cards, so can build meaningful points in a hurry. While only 1 SPG card with paltry bonuses (biz/personal).

MRs transfer in 1K increments and usually transfer instantly. SPG can take weeks and have to transfer with 20K increments to get the airline bonus (not very handy if you just need a few miles - and if you have to wait, your award availability may disappear by the time you see the points in your account).

PRG gives 15K MR bonus with $30K spend. Put $30K on gas/grocery and get 75K plus signup bonus (or 105K plus bonus if spend $30K on airfare). What will SPG get you for $30K spend? 35K if transferred to airlines (up to 80K difference, which is massive). Then if you can use Amex transfer bonuses, you can goose your miles even further. You can literally get ~4x more points per $ spend on PRG than you can with SPG.

PRG has higher AF ($175), but for serious spending, worth every penny (best Amex card by a country mile for my uses - the rest are only worthwhile for signup bonuses as there are few bonus spend categories).

That said, the Amex Blue 6% unlimited at grocery was a gem of a card. Pity my unlimited expires end of next month. Only get high 5 figures cash back from the card

About the only competition for the PRG is the Ink Bold/Plus for MS. And that's only because Inks can generate 5x points thus are fast to generate points (despite slightly higher cpp than PRG with 2x at grocery).