Thank you for your replies.
With so many variables with tyres, riders, road surfaces etc, etc, I know this won’t get a conclusive answer and I am sure personal preference comes into play too.
There have been days when I have stopped my bike and checked the wheels were turning OK, just simply because it felt hard work, when in fact all was wrong was I was having a bad day
!
Having given this much thought I can only think the difference, if any, would be marginal and other influences such as weigh of bike, tyres and road surface etc have a much bigger influence.
For my money I will be going 26” as I still see the known benefits out way any alleged shortcomings.