Howard Oakley, on eclecticlight.co:
Even for a beta, Big Sur has a voracious appetite for disks: as one leading developer, Jeff Johnson of @lapcatsoftware, discovered, when updating from the first to the second beta, macOS swelled to 27 GB in size. This is the result of its use of snapshots.
I did iOS 14 and iPad 14 Public Beta over the weekend. Will likely hold on Big Sur for a while longer.