I notice a lot smoother engine performance with 93 vs 87. IMO even with DI, 87 on 12:1 compression especially with high ambients is asking for trouble. It doesn't do that low RPM "buck/bog" like it did from 1200-2500 in a higher gear on 93, and I feel it pulls a LITTLE harder - especially down low.
I'm going to keep running 93 anyway. Has more detergents to keep the intake valves carbon free (characteristic of DI engines).