I generally avoided one type of seat - always thought the first seat up the step, was poor for legroom. The Nationals and Lynxes were bad if I remember right, due to the position of the metal railing.
The seat behind was poor on a National, due to the location of the wheel arch positioned between the two rows.

Loylnes are bad at the front upstairs.

Always prefer the facing seats on a single decker.

The old deckers had seats backing onto the window in a bench style that I liked.

Back in the day, it was always the back seats, decker or not.