Out of the alphabet titles, clearly the WBC is the most credible. Mainly because it has the most champions that are also recognized as the real/The Ring champions.

THere champs are the same at the The Ring/The Real champ in

Crusier
Lt Heavy
Middle
Welter
Super Feather
Junior Feather
Jr. Fly

I dont think any other organizaiton comes close.

Then you have the WBO and IBF

Last would be the WBA which has become a complete joke, by having up to 3 wba champs per division. And there regular title. A disgrace.