I have one of the Gladiator (7ft 4″ x 7ft 3″) sheds, which I got after my wooden shed got broken into on several occasions. I fitted a ground anchor on each side and there’s plenty of space inside for my bikes and garden stuff. I’ve noticed some condensation at times but it doesn’t seem to have cause many problems.
The bike stores will probably be different but the sheds are very unsubtle, mine really sticks out like a sore thumb compared to my neighbours’ sheds, possibly because they’re pretty tall and they have no windows. Also they can be a bit noisy if you bump a bike too hard against a wall or an open door catches in the wind. However the main thing is that they feel tough and they look tough, which is probably the main reason nobody’s tried to get into mine since I got it.