[goobatrooba]

I agree on the rest but don't see why it would be heavier. If you have more feet standing at any particular moment the load would be more distributed, i.e. movement should be easier with more legs (depending on leg weight of course).

[solid_fuel]

You're confusing (pressure on the ground / surface area) with overall weight (the sum of all pressure on the ground). Having more legs is heavier simply because now you have additional struts and motors that you didn't before, those items are linear with the number of legs, and the total weight is weight_of_leg x num_legs.