The earlier LSO ones of M1, M2, and M9 are preferable to the later Chicago ones. John Kim likes Solti's earlier Concertgebouw M4 very much. Personally, I don't care for any of his M5 recordings, and he was notoriously awful with M3. The CSO M6 and M7 are decent. That said, the timpanist can't play his opening flourish at the start of the finale of M7, and it's all pretty much downhill from there. The notes are all there, but it's like somebody who puts sentences together in a way that's totally incoherent. The M8 is still famous today, although it's certainly not my personal favorite.
By the way, the worst Mahler concert I've every heard/seen was an M5 with Solti and the CSO, on tour at Davies Hall. Just plain awful!