IIRC, there was a thread in the General Discussion forum a while back about comparative, semi-dual, illusionary and look-a-like relations, about who preferred which ones. As far as I remember, accepting subtypes generally preferred comparative and illusionary relations, while producing subtypes generally preferred semi-dual and look-a-like relations.

Also, I personally value mirror relations over activity, although that's probably coloured by my experience rather than a general preference.