Chang because he's better in virtually every area save power. And while Carbajal is good enough to have his moments, I think the Korean Hawk showed enough durablity throughout his to weather them and emerge with the clear decision.
Carbajal would win. He had skills and hit to hard. Defensive types that lack power have a tough time matching up with him. In addition Carvajal beat Chang opponents that defeated Chang. Who you ask? [url]Muangchai Kittikasem[/url] [url]Humberto Gonzalez[/url] You can make a case that Kittikasem and Gonzalez were the best fighters Chang fought.
Chang is too quick on the draw and dynamic. He would just figure that he could outspeed Carbajal, and would then pick his spots accordingly for a clear decision. Carbajal has a KO chance over anyone at this weight, but seeing how well Chang dealt with Torres power, it is unlikely. On a separate note, I think Chang would also do the same to Yuh, and that it wouldn't be the ATG war some purport it would've been.
What is Chang's listed reach? He's got real short arms. Could have a 61" reach. Carbajal is also very skilled, taller, longer and hits much harder. Chang is out matched up close, and would have no answer to Carbajal's power. Cleary he hits harder than Torres, who pretty much lost all of his big fights.
I do agree that Carbajal was a more dangerous puncher than Torres. Pretty much better than Torres in every way imaginable.