Is it more difficult to renovate co-op vs. condo?

Depends on how strict the co-op board is. Some restrict work to summers, for instance.

Co-ops have a higher likelihood of having rules, but the specific rules matter.

Co-ops might have more stringent alteration agreements than condo buildings, but don't know about that.

Physically, co-ops tend to be pre-war, with solid plaster (gypsum block) walls, whereas condos tend to be 1980s-or-later with metal-stud-and-wallboard walls, so moving walls/doors/etc. in a co-op tends to produce more debris. Debris is expensive to haul out and dispose of. Rewiring a condo is easier for the same reason: you can fish through the walls instead of chopping through plaster.