I honestly think it makes no difference. I started with a 5/8 full hollow which shaved great and not long after got myself a 7/8 wedge which I also love.

As long as you get a good make of blade that will take and hold a shaving edge I think you'll be fine.

As B says, those recommendations are mainly because they are middle of the road in terms of size and grind allowing you to go either way after that. If you're anything like me you'll end up getting a load of different sizes to try out anyways!