I think you can over do this shed thing if it is really just a shed. If this is big enough to set up a shop out there it may be worth pulling in a 60a feeder but most people will never do more than store some stuff and maybe want to plug in some hand held equipment.
If you really do think there is a future expansion in mind, pipe it, but to keep the bid reasonable I would still go with four #10 conductors.

Did anyone take the drastic step of asking the customer what they want?

[Linked Image from gfretwell.com]

Greg Fretwell