My understanding aligns with Giga's. You can't reattach branches, but you can always cut a branch (and the wire) off later.
So, when you're doing your initial styling, if there is *any* chance (like even 0.0001%) that you might want to keep the branch, go ahead and wire it. The wire will let you move it out of the way and/or into a better position as you work on the tree. If, at the end of the wiring/styling you can't find a use for it, cut it.