From a practical and durability point of view, I think a plastic shed is very sensible - no painting, no maintenance.
But from an aesthetic and - how shall I put it - a world view on the use of plastic and the drastic plastic pollution in the sea, I think a recycled wooden shed would, not alone be aesthetic in the garden, as it could double as a summer house, but also be very durable and you would be re-cycling the wood already in use. I know the wood would need treating from time to time. A small price to pay, though, don't you think?
So that's my contribution to an answer, in spite of the fact I bought a very durable plastic shed a number of years ago and gave it away to someone else, when I left my garden, due to moving house.
Because I now don't 'own' a garden and rent an allotment, I'm tempted to 'have' another shed - though I will make a concerted effort to create a wooden one from recycled wood.
After all this preaching I would want to, wouldn't I?
I happen to like sheds and think every garden should have one, though it can be constructed in a creative pleasing way and help the environment.
Thanks for the question.