I went from a ZI Star Spec (old model) to a wider Nitto NT05. I have logged Data in similar conditions that average me at .5s slower per lap on the wider setup.
I think the answer in your case will be "it depends". I know the R1R is brilliant for autocross. However, I have had reliable sources tell me that they won't put up with the heat on a track due to the tread block design (vs. a ZII). So if you're running Time Attack/Time Trials and work them right and/or shave them, you might end up with one fast hero lap in a session before they get greasy. With the ZI I would typically see a nice bell curve with lap times in a session building "up" to ~3 laps that were legit fast, with a warm up and cool down on either side.
So if your lap times count for something: sure, may as well experiment with the wider setup. If you're just out there to have fun, but want to do so on a good tire, the Dunlops may be the way to go.