It depends. Expended energy/m is higher but space usage is much lower. For walking you arguably don't even need a paved path while (non-sport) cycling needs a somewhat even surface and places to store and lock the bike. It's not nearly as bad as with cars but even with cycling, space usage can become an issue in very densely populated areas; the Dutch don't build massive bike garages because it's cool (okay, maybe also a little of that) but because it's a necessity.
If it's near enough to walk, it's usually better to just walk.
I don't see why those two features should be exclusive; both should exist and have their own purposes.
Defederation is for nasty instances whose users violate basic etiquette such as exploding-heads or hexbear. No tolerance for the intolerant.
Instance blocking should IMO be reserved for potentially disagreeable instances that aren't degenerated shitholes. Places that can behave themselves but are about topics a large portion of users might personally not like or aren't interested in such as feddit.de/nl/uk/it/..., programming.dev, startrek.website or lemmygrad.
Edit: Grammar.