Shimano pedal bearings are generally excellent.
I’m considering moving to SPD-SL myself, mainly because Look Delta cleats wear out so fast (a few months) and are getting hard to find (i.e. expensive) into the bargain. Plus, I’m getting more squeaking as more of the aluminium platform wears away where the cleat rubs against it.
The Dura-Ace SPD-SL pedals have a roller bearing in addition to two ball bearings unlike the other SPD-SL pedals that lack the roller bearing. (However, the latest PD-R9100 may have dumped the roller bearing for a simple bushing. I’m not sure about that and would appreciate confirmation from someone who’s looked inside.)
For that matter, I don’t fully understand the Ultegra, etc., bearing arrangement since I cannot find a 2-D section view to see how the parts interface. Shimano’s 3-D exploded view obscures the relationship between parts. Is there a metal bushing in the middle?
At any rate, the Dura-Ace pedals have a lower stack height because of this bearing arrangement. Not sure if that matters to you … or anyone.