Their resumes are basically equivalent, although I'd give Manny a slight edge as of right now, although should both win their next fights, I think the Mosley win would push Mayweather's just ahead. The easiest way to look at is the number of hall of famers they have both faced.

Pacquiao: (Certain HoFers) Marco Antonio Barrera, Erik Morales, Juan Manuel Marquez, Oscar De La Hoya (Probable) Ricky Hatton, Miguel Cotto, Chatchai Sasakul (Possible but unlikely) Jorge Solis, Oscar Larios

Mayweather: (Certain HoFers) Genaro Hernandez, Diego Corrales, Juan Manuel Marquez, Oscar De La Hoya (Probable) Jose Luis Castillo, Arturo Gatti, Ricky Hatton (Possible but unlikely) Zab Judah, Jesus Chavez

So that's pretty close to even, but with Pacquiao having a slight edge. Part of the whole 'ducking' issue also comes down to where people watch fights. Anything below Lightweight doesn't get much attention, even among many fans. You can make an argument that Mayweather should have fought Margarito or Cotto, however you can equally make the same argument for Pacquiao with the likes of Joan Guzman, Nate Campbell or Humberto Soto at the lower weights. In the end, both have taken more than enough dangerous fights and have probably the best resumes in the sport and once their careers are over, the fights they 'ducked' will be forgotten in favour of realizing just how many dangerous opponents they fought.