The honest difference between the two comes down to moisture, storage and when you intend to burn it.
It comes down to moisture
Freshly felled wood is roughly half water by weight. Kiln dried wood leaves a controlled process reliably under 20% moisture. Properly seasoned wood is air dried to around 25%.
What kiln dried gets you
Consistency, easy lighting, a quick rise to temperature and less smoke and tar. Ready to Burn certification requires 20% moisture or under.
What seasoned gets you
A lower price and good fires when it is stored somewhere dry and airy. It is best bought in summer and allowed more time before burning.
Which should you choose?
Kiln dried for immediate, consistent use or limited storage. Seasoned when you have a proper store, buy early and want a lower price per cubic metre.