Rockwool vs glass fibre and availablity of 150mm thickness

[benawhile]

I have previously asked about materials for loft insulation and have come down in favour of insulation roll, loft legs and standard loft board.

I want to increase my loft insulation from 4” glass fibre to 10” and retain access and storage using wickes 7” loft legs and standard loft boards.

Problem is according to all sources I can find, rock wool is a superior materila to glass fibre and while I would like to use it, I can't find it in 6” thickness, only 4 or 8, (100mm and 100mm)

There is something called rockwool rollbatt at Jewsons

 

https://www.jewson.co.uk/building-materials/thermal-insulation/rock-insulation/products/RWRB1503/rockwool-rollbatt-365m-x-400mm-x-150mm-pk-of-3/

 

Could I use Rockwool “rollbatt “ as if ti was standard roll to insulate across the joists in my loft, and board over it using loft legs?

Is rock wool available anywhere in 150mm

or

am I misinformed about the superiority of rockwool?

 

Finally a gripe:

It is stated on US websites that rockwool has a better u value, repels moisture where glass fibre soaks it up, and is more fire resistant.

It seems little has changed since I insulated my last house in 1979. There are the same two basic materials, glass wool and rock wool. Glass wool, confusingly also called glass mineral wool for some reason, confirmed by all sources as inferior to rock wool, is nonetheless almost universally available by all manufacturers, but rock wool is only made by one firm.

Even products like Knauf Earthwool, which sound as though they would be more natural, and actually do feel more natural, are made of the same old glass “mineral” wool