Worth changing from 100mm to 125mm duct & vent?

[tuck1s]

The bathroom extractor fan is a ceiling-mounted rectangular Greenwood Airvac, approx 23 years old (original). It still works but has always been quite noisy.
It vents via flexible 100mm duct travelling through the loft space and out of a soffit vent with a gauze filter inside, also 100mm.

I was pleased with changing the other bathroom (shower room) to a QuietAir 100T. If I now change this one, I could fit another 100T, or enlarge to a confusingly-named "120T" https://www.airflow.com/product/quietair-range/9041498 which appears to use 125mm ducting and have much higher flow.

I'm assuming it's simple to enlarge the ceiling and soffit holes up to 125mm? I have previously tested the soffit boards for another project and they don't contain asbestos (I sent a sample away for testing).

The duct run is about 1m. Would I notice any performance difference with hard duct or may as well just use flexible for such a short run?

 

[sparkwright]

I would stick with the 100mm ducting, and fit a 100mm fan.

It's not worth the effort.

 

[Murdochcat]

Put an inline fan in the loft when the existing one goes wrong AND check you have airflow under the door to ensure the fan can such air into the room too