If I didn't have graphite Recoils I'd have Nippons....or possibly KBS, but I might give the edge to Nippon.
One of my golf buddies sprung for a set of Miura irons a couple of years ago and the fitter recommended TT AMT Red shafts and I told him to ask for Nippon, but he got TT. He's broken and replaced 4 shafts already and 2 of them just broke under the grip in his backswing.