I've had TKC 70 on a 1200 GS, and I thought they were very good, they lasted well too, didn't seem to square off so quickly, maybe they have a different compound in the centre, ?
I fitted the Avon Distanzia tyres to my 1987 800 GS, ( Think front was 21"not sure) they were brilliant for green lane riding , I remember not being to happy with them on the road, only happened a couple of times, could have been the conditions at the time but it did put me off buying them again,
I do think the std tyres will take some beating though,