Well as I said earlier, it is swings and roundabouts.
Would you pay £100 per hour* for a C172 Hobbs, or £130 per hour flight time? If doing a long flight, then the £100 per hour is going to be cheaper, if doing small hops for your £100 burger then you will pay more for the flight time.
Whatever way it is done, one thing is sure that the operator won't lose out. If a club charging £100 per hour is forced to charge flight time, then you'll end up paying £130 per hour anyway.
What you have to watch is the club that charges £130 per hour hobbs when compared to one charging £130 per hour tach.
*NB: Made up prices, I have no idea what it costs to rent a 172 these days.