Don't think it really matters.
Some riders like the recovery day afterwards, some work Sat's, some work Sun's, some work nights and can't do Sat unless they take a Fri night off.
Some are lucky and work 9-5 Mon - Fri or are retired and can do all a lot of rides.
Trains are often better on a Sat for those who use them.
If a rider fancies doing the ride they will find a way and work round the Org.
Questions like this will give you an answer from all of the above groups and not likely help in your planning
Thank you for being an organiser though