A search for OWO will find lots of discussions about the issue, and this may get merged with one of them at some point.
There are some risks attached to OWO and only you know if they are worthwhile.
Don't imagine that there's more to be made: some clients want OWO, some want OW (and some won't see anyone advertising OWO), but most don't care so long as you have their penis in your mouth.