The spell functions similarly to an Angel Banishing Sigil, but it is implied that its effects are much more potent, as an Angel Banishing Sigil only banishes an angel far away from its initial location on Earth, whereas the Angel Banishing Spell ejects the angel from its vessel and banishes it back to Heaven. Considering that Alastair considered banishing an angel to Heaven as an alternative to killing them off ("I really wish I knew how to kill you, when all I can do is send you back to Heaven."), it is likely that the angel would be unable to return to Earth immediately, if at all.