I have been using the square taper since I started riding nice road bikes in the early 1970s because up until about the past 10 years, that was all that there was. I still use one. Campy and I never have had any lack of stiffness or chain ring rubbing the front derailure. If that were happening, it would be a function of my bottom bracket shell flexing and a less than rigid frame. With sealed units, you don't or should not have deflection. In the old days, that would happen until I installed my first Stronglight sealed BB and wow was that nice and tight. There is all this discussion about how the newer BBs are stiffer than the old square taper and mechanically that should seem to be the case. But, again, I have no movement or flexing of my crank on my square taper BB. The frame is a Merlin titanium, and not an overly stiff aluminum or carbon fiber.