For the longest time the answer was: MKS Mapstage
clipless. They had a unique “turntable” cleat that used sideways rotation for entry & exit. I used these for 20 years & watched on the sidelines as new clipless designs evolved. I would repack the bearings and polish the bodies every winter - very satisfying since the bearings could be set up with near zero play while still spinning smooth.
Then about 2 years ago, Iooked at the weight of the pedals and realized how heavy these MKS’s were compared to modern (road) offerings.
So I bought some Shimano PD-9000’s and mounted the yellow SPD-R cleats to my size 46.5 Sidi Genius 5’s. As much as I owe gratitude to the MKS’s for all the good service - these Dura Ace PD-9000’s are fantastic! I love them. They are much lighter, fully rebuildable and cleat engagement is fantastic. The have lower cleat stack height, keeping the ball of the foot closer to the pedal axle. This feels better to me & I’m sure there is some biomechanical theory why this is the case.
The PD-9100’s are more of the same goodness and I have a pair of these on another bike.