Difference between Vredestein Wintrac Xtreme 4 & Xtreme S

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Can anyone help with this?

Want to put Wintrac Xtreme 4 on the Mrs' Evoque (245/45R 20) but the tyre company can only source Xtreme S and I can't find the difference online.

The 'S' seems to be more sporty (not really needed on an Evoque) but does that mean they have lower winter performance? (which is what I want to avoid)

Thanks

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Tyre place just called back, they don't do 245/45R 20 in an Xtreme 4, so it's the 'S' or another brand

Still interested to know what the difference between the '4' and the 'S' is though

They are trying to sell me Pirelli's instead