That's for the bit of clarification folks, I still don't see how this new no-buckets thing is different to the old progressive mode, but maybe there was some core wastage in progressive mode they got rid of?

In p12 sometimes I use bucket renders and sometimes I use progressive, and saw no time difference in render time with them previously. I did however a few times see a visual difference in the render when the same exact scene was rendered in progressive mode versus not in progressive mode - this may have been a bug that has been fixed?

I still think it seems disingenuous to try and compare render times of P12 with P13 if the render settings (pixel samples and adaptive sampling thresholds) are different. Comparing apples to oranges basically. Are the render times different with CPU renders or is it just GPU renders that have benefited?