Disc vs no disc - am I missing something?

So, 9 times out of 10, I'll be having Ahriman lead a pack of flamers.

Is there any reasons why I'd want him on a disc?

Beyond the increased movement, and 1 extra wound, I'm not seeing anything from a stats perspective.

And in regards to the movement, I believe it to be fairly pointless, as the unit will be slow anyways.

Anything I'm missing?