That said, a lot of guys do "harder" dubs first, in my crew some guys did dub cork 10 and 12 before doing dub back or dub front! It depends on what you want to learn, or think is good looking, and what you feel comfy trying! If you're rock solid on corks or sw flips, mabye dub cork and a sw dub 9 is a natural selection for a first dub!?
I did dub front and back first, i tried kang because i felt comfy on flats and rodeos, but found that very hard to do! I'll probably gonna try a dub cork 9 or 10 next, as i belive it might be easyer for me to learn (no claim).
You've seen phil doing sweet slow corks, He also do not do the biggest rotations!
Don't you se a floaty dub 7 or 9 fit hes trick bag?
Point: there is no harder dub! they are all hard, and it depends on your other tricks!