ALTER will also force a recompile of the entire procedure. Statement level recompile applies to statements inside procedures, eg. a single SELECT, that are recompiled because the underlying tables changes, w/o any change to the procedure. It wouldn’t even be possible to selectively recompile just certain statements on ALTER procedure, in order to understand what changed in the SQL text after an ALTER procedure the server would have to … compile it.
For all objects ALTER is always better because it preserves all security, all extended properties, all dependencies and all constraints.