I think KT is the greatest 140 pounder ever. Pryor could be countered and didn't hit had hard as tszyu but was the "buzz saw" type beast. Tszyu SD 12. 15 rounds might be a different story?
The KT that was motivated and realised he had to continue to work, i.e. Ruelas to MItchell fights (1998-2004), sees him being almost unbeatable at 140 IMO. Did I mention IMO? Alexis couldn't handle KT in this period. Too big and just too harder a punch. Nothing against Arguello but against the elite and KT and Pryor are 1 and 2 (order to be argued and analysed) at 140 ever, he just wasn't quite there. At 130 he may be the best ever(?).
I know I said the Tszyu of 1998 - 2004 was amazing but narrowing it down more, to three fights, being, Ruelas - Hurtado - Gonzales, Tszyu was beyond sublime. In this period he was unbeatable. Vince got him pre and Hatton post this period and when he walked through Shambay in '04, he was most likely past his best and look what happened.
I totally understand picking kosta, but i'll go pryor by decision in a close fight with activity getting the nod over power.