Wins/loses at different weights, does it matter?

I was having this debate in another thread but i am strongly willed on this one. The case in point was if a fighter loses to another at say...middleweight. Then the fighter who lost goes to lightheavyweight and wins the undisputed championship. Meanwhile, the fighter who beat the guy who has won the UNdisputed title eventally moves up to lightheavy. NOW.... This is the problem. Would you rate the undisputed lightheavyweight champ as number one or would you rate the guy who beat this champion by virture of his moving up two weight divisions as number one? The case in point earlier was Manny Pac and Barrera. barrera is undefeated at super featherweight. Morales was Linar champion when Barrera last beat him. Barrera has won the WBC/IBF titles to boot. Manny Pac's first fight at super feather was against morales and he lost. He did did win the rematch in great form. However, and remember the weight issue i`m eluding too. Manny lost to Barrera's hand - me - downs. Then he beat Barrera's hand - me - downs. As creditable as those wins are, Manny has not beaten a world champion at super feather, only a disposed one, who beat him first time round. YES, i appreciate that Manny beat Barrera at featherweight and in good style. However, regardless of your fan approval, how could one think Manny Pac as the true champion when all he's done at SUPERFEATHERWEIGHT is beat Barrera's left overs? Believe by all means that Manny Pac will do unspeakable pain to Barrera when they meet again but untill that day you must rate weight divisions independantly of accomplishment achieved in alternate weight catagorys. Barrera is 3 - 0 - 0 ( 1 ) at superfeather and has two title belts. Manny p, despite one good win over Morales is 2 - 1 - 0 ( 2 ) at super featherweight and he has not beaten a champion, sanctioned or linared. I`m not hating on anyone, i just want to clarify that if were gonna have weight divisions then please reflect on them as they are, divisions.