I have both the Amex PLT and have been in the new FL when flying internationally...

My take...

Food: About the same-better in FL if you have FFD, maybe slightly better in Centurion for the “normal areas.”

Booze: Centurion Lounge... I personally prefer a good bar to the self serve liquor in the FL... But maybe that’s reflective of my bartending skills.

Seating: About the same, both can be crowded at peak times... I think the seats are more comfortable in the Centurion lounge but I think it’s generally busier too. One nice thing about the Centurion Lounge is that the lounge staff will come to your seat and ask if you want/need any food/drinks refills. Haven’t seen this in the FL.

Amenities: Both have showers, Centurion has the spa (but tough to get reservations).

Views: Better from the Flagship Lounge... View of the tarmac vs. view of check-in area.

just my $.02