However if the ILS glide path is available it is far better to stay on that glide slope until close to the flare because of the limitations of visual approach slope systems and their siting to the side of the runway.
As the GP can (and frequently will) bend up and/or have significant structure past minima, that's not something I'd recommend. Besides, there's quite a bit of damping on the receivers, three second time constant. You're acting on old information. Doesn't matter much with a mile to go, but in close, well...
The PAPI shall provide correct information up to eight degrees from the unit in azimuth, meaning you should pretty much be in the roundout by the time you lose PAPI guidance due to the siting of the units.
Cheers,
Fred