It really does come down to synergy. My default tube, a Holland-made E188CC, has a glorious wet mid range with great liquidity and flow. Putting the 01 in, there was less flow and the mid range was a bit drier. Putting the 02 back in, the flow came back and mid range was glorious again. Some example tracks: James Blake's Overgrown album - 'Overgrown', Robert Glasper's Black Radio 2 album - 'Calls', and David Gray's White Ladder album - 'Please Forgive Me'.
Again, it really does come down to synergy, and given my ears and gear, the 02 and the E188CC are a match made in heaven. :)