Plasterboard Vs MgO board U values

[MrsRenovator]

Just wondering if anyone knows how the U value of PB compares with MgO board?

Let's say:
9.5mm PB vs 9mm MgO board

I'm really limited for space on the top of a window reveal and want to know if using MgO would make any difference to the insulation level.

What do you think?

Thanks

 

[oldbutnotdead]

Google is your friend, U value of plasterboard is pathetic. No idea about MgO board. Marmox is quite good but a bit dear per sq m

 

[^woody^]

More or less the same.

 

[MrsRenovator]

I googled. Can't find the answers to compare. Thats why i asked.