There's negligible difference between the two in my Swift, in similar conditions, on the economy front. The calculated MPG often hovers around 40; I did some 300 miles recently on a tank of 95, turned around and did the same distance on 97. Worked out as 38.97mpg on 95 and 38.19mpg on 97. That's been repeated since, approximately, too.
It has historically returned its best on super, though, and I did recently get a batch of 95 that it was particularly unhappy on – plenty of low-speed knock. It is quite sensitive to fuel quality, mind, but I think it was probably just the fuel from that particular station. It hasn't exhibited such significant issues on subsequent tanks. Regardless, I prefer to opt for the best fuel available; I've just had to use 95 a few times due to availability issues.
The Corvette isn't troubled by it and returns similar economy on 95 as it does on anything better, and runs just as hard on either. But then that's just a simple naturally aspirated engine with an unremarkable compression ratio. Again, I'll usually stick the best available in it if possible, though. Every little helps...