The only argument I can think of is that the winner should face the winner of Perez-Mares to establish lineage, but both those guys are more up-and-comers than established forces in the division. I'll say yes. :good
For me the best two bantams in the world are Hasegawa and Perez,but this is a great fight and the winner has to face Perez next if he wants to be considered the main guy at 118.
WInner of Hasegawa-Montiel vs the Winner of Mares-Perez, I think Anselmo Moreno would be the legit #1 contender to fight the Champ of those fights. He deserves it before Darchinyan.
Hasegawa will destroy Montiel at this stage. Perez vs Hasegawa will confirm whom the best in the divison is IMO. Mares is shocking and will get battered by Perez, who looks very good at 118.