Here is my .02. You are going to waste at least 45 minutes or so in getting off the plane upon arrival, go to the restroom and finding a decent spot to spend the night, that takes time off from your layover. I prefer the longer layover where I can spend the night and rest on an inside airport hotel vs sleeping on the terminal. At least you can get a longer rest & freshen up prior to your return flight. As mentioned above, most lounges will be closed, so they are out. If you are willing to spring the $$ for a hotel, go for the long rest in Madrid instead of AMS.