I used to run the M/T ET Street S/S 315/60R/15 till it was discontinued, so made the switch to ET Street S/S 295/60/15. I haven’t noticed any real performance drop off, since I made the switch.
I race in Street class, where by we have to race as we would be on the street, with exception we are allowed to use E85. I still have work to do on rear end adjustments, so 60 is only 1.23, best pass to date is 7.40@ 205. Another guy in my class has been high 6’s @215. So a great tyre, can’t believe the 275 would be that much different