How does Linen compare to other natural fillings?

I am considering a John Lewis Natural Collection Linen Mattress - the current one has 5000 springs, but I can see a few others available new on places like ebay with 4000 springs.
So, what is there to say about linen flax (which the more detailed info refers to) compared to other fillings. The top layer is linen missed with cotton and then there are 2 other layers which are wool and cotton, followed by wool,cotton and hemp. After that there is a layer of the mini HD springs.
This linen model seems to be one up from the Cotton Natural mattress and one down from Egytptian Cotton and Yorkshire wool models.
Wondered if linen will give a firmer or softer feel and if it has any merits or disadvantages over other fillings.
Many thanks.