I don't suppose it'll make much of a difference in your decision, but:
the whole idea of fog lights is to have a lighting source that will penetrate (somewhat) the fog without illuminating the water vapor to the point where your field of vision is further impaired. you may have noticed that, if you turn your high beams on in thick fog, you can usually see nothing more than a wall of white fog. ...this is why, typically, factory fog lights are wired so that they turn -off- when the high beams are on.
so, wiring the fog lights so that they -only- illuminate when the high beams are on is, well... counter-productive, at best.
2001 Ranger XLT 4.0L SOHC
Silver Frost w/ Dark Graphite interior
Summit 3" Body Lift
31x10.50 A/T tires
Explorer overhead console
Explorer auto-dim mirror
Aux1 & Aux2 inputs on factory AM/FM/CD/Cassette
Door-dinger silencer button
Seamless retractable roof and passenger-side ejection seat with steering wheel mounted controls and safety interlock