Ok, let me start off by saying this only applies to tuned users only.
GM's official fuel rating for the Cruze is 91 Octane, so running 93 Octane most likely won't make a difference. However, I have noticed an increase in performance between 91 and 93 octane on both eco and sport mode of the trifecta tune.
For starters, 91 Octane is only available through select retailers on the east coast. Sunoco is a popular one that offers both 91 and 93 octane. I made the switch to 91 Octane from 93 two years ago because Trifecta told me it was "safe" and there is anywhere from $.2 / gal to $.10/gal savings between the grades depending on the station. I first noticed last summer that my dyno was performed on 91 Octane, which resulted in stock and trifecta achieving closer numbers than anticipated. I aslo noticed my quarter mile and 1/8 mile times dropping from when I first bought the tune and was blindly using 93. I consistently run a 10.2 @ 70 and 15.8 @ 87 in the eigth and quarter mile on 93 octane. Since I've been running 91 for about a year now, last year my times were around 10.5 @ 67 and 16.1 @ 85 and I couldn't figure out what the **** was going on. I thought it was just heat soak and my cool air intake not doing anything.
About two weeks ago I grew some balls and put some 93 in the take and was floored that there actually was a difference. The car is stronger especially in the summer on 93. I emailed Trifecta and Vince told me when he crafted the tune he was running 92 because that is all that is available to him and that although 91 is "safe" the car is most likely pulling timing even on 91. 92 Octane maybe the "high octane" table threshold for the higher boost of the tune.
Conclusion: don't be a cheapa$$ like me. Run 93 Octane if you are tuned and sorry Cali boys you may want to invest in some octane booster.