Carvoeiro any day!!

We are all different. I would go for Praia da Luz.
What do I mean "would"? I liked it so much I bought a house in Praia da Luz

If you are thinking beaches, the beach at Luz is rather bigger than the beach at Carvoeiro. Carvoeiro is also much more hilly than Luz. The old part of town and beach are built at the bottom of an old river valley surrounded by steep hills. Many of the resort hotels are on the tops of said hills, so uphill on the way back from your day of sun and sand. Not to say that Luz is flat, it's not and some bits are quite a climb also.

The layout of these resorts is very different. Going to eat at Carvoeiro we found difficult as the narrow winding streets make it impossible to park near the resturants so if you plan to eat out a lot you might want a villa or hotel within walking distance of the centre. Parking in the height of the season isn't brilliant in Luz, but it was definately better than Carvoeiro.

Difficult one really both are nice resorts.