Table for my mill

[Pete O]

I don't think you will have too many worries regarding strength either way, BUT... cutting and welding the corners at 45degrees would give you a stronger join, as there is more length of weld in the joint, plus putting the legs under the corners would be supporting both sides of the weld so no vertical shear load on the weld. If you ended up going that way, a triangular piece of plate under the corner and then the leg under that would give you maximum strength.