We've had a few over the years...
Benoit (no longer exists) - had wooden seats!
T17, T18 mostly. As others have said T17 for the lack of pillars and the great facilities, slightly cheaper amenities and if the weather gets bad (which of course it never does!!!) you can hunker down inside if you really feel the need and watch on the screens. There are showers, although we haven't used those ones for a few years now - the ones on most campsites seem to be kept clean, I'm sure ours were cleaned 3 or 4 times a day this year!
We've been in Dunlop - although that was 2007 when the rain gods were truly busy and the first year the Danes came en masse. In addition we were 3 fields 'in' on Beausejour and it was a mudbath. Never again!!
We've had seats in the pits grandstand - you get great overhead views of pitstops from there.
I must admit I like the Test Day and practice sessions where you can sit in various grandstands and try them out. I've been in the Mobil grandstand and the one that is/was open air at the Ford Chicane.