I favour 1:2:1 up to about 1.3:2:1.3
This is based on what sells and not what an individual prefers.
For example a 2 ct center with 0.5 ct each side is a solitaire with shoulder diamonds that would best be set slightly lower and possibly with more tilt - axis radiating to the center of the ring.
The side stones should be set a little lower.
A classic 3 stone has the girdles almost touching and the axis of the diamonds usually points to the bottom of the band.
That is exactly how mine is set. I always thought of it as classical three stone ring. But makes sense!