I would have to go with Manny Pacquiao when you consider all of the weight divisions that he's gone through. Here's a look at the former world champions that each of them has faced with the results of the fights and when they took place:
~8/2/1997- W12 Phillip Holiday for IBF lightweight title.
~5/9/1998- TKO8 John John Molina to retain IBF lightweight title.
~11/14/1998- TKO9 Jesse James Leija to retain IBF lightweight title.
~6/17/2000- W12 Oscar De La Hoya for WBC welterweight title.
~1/26/2002- L12 Vernon Forrest for WBC and linear welterweight title.
~7/20/2002- L12 Vernon Forrest for WBC and linear welterweight title.
~2/8/2003- NC3 Raul Marquez (non-title fight).
~9/13/2003- W12 Oscar De La Hoya for WBA and WBC junior middleweight titles.
~3/13/2004- L12 Winky Wright for WBA, WBC, IBF, and linear junior middleweight titles.
~11/20/2004- L12 Winky Wright for WBA and WBC, and linear junior middleweight titles.
~2/25/2006- TKO10 Fernando Vargas (non-title fight).
~7/15/2006- TKO6 Fernando Vargas (non-title fight).
~2/10/2007- W12 Luis Collazo (interim title fight).
~11/10/2007- L12 Miguel Cotto for WBA welterweight title.
~9/27/2008- KO12 Ricardo Mayorga (non-title fight).
~1/24/2009- TKO9 Antonio Margarito for WBA welterweight title.
~12/4/1998- KO8 Chatchai Sasakul for WBC flyweight title.
~9/17/1999- LKO3 Medgoen Singsurat for WBC flyweight title.
~6/23/2001- TKO6 Lehlohonolo Ledwaba for IBF junior featherweight title.
~11/10/2001- DTD6 Agapito Sanchez for IBF and WBO junior featherweight titles.
~6/8/2002- TKO2 Jorge Julio for IBF junior featherweight title.
~11/15/2003- TKO11 Marco Antonio Barrera for linear featherweight title.
~5/8/2004- D12 Juan Manuel Marquez for linear, WBA, and IBF featherweight titles.
~3/19/2005- L12 Erik Morales (non-title fight).
~1/21/2006- TKO10 Erik Morales (non-title fight).
~7/2/2006- W12 Oscar Larios (non-title fight).
~11/18/2006- KO3 Erik Morales (non-title fight).
~10/6/2007- W12 Marco Antonio Barrera (non-title fight).
~3/15/2008- W12 Juan Manuel Marquez for linear and WBC junior lightweight titles.
~6/28/2008- TKO9 David Diaz for WBC lightweight title.
~12/6/2008- TKO8 Oscar De La Hoya (non-title fight).
~5/2/2009- KO2 Ricky Hatton for linear junior welterweight title.
~11/14/2009- TKO12 Miguel Cotto for WBO welterweight title.
Pacquiao was the fighter of the year in 3 of the past 4 years and has won titles in 7 different weight divisions whereas Mosley has won titles in 3. They have both fought the best in their respective divisions but I think Pacquiao has had more success. They both have some questionable decisions (Mosley in the rematch with Oscar and Pacquiao in the 2 fights with Marquez) but the majority of the big fights they fought, they won and they looked good doing so. Now that they are in the same division I would love to see them fight each other but Pacquiao has business to attend to in Joshua Clottey and it looks like Mosley may finally get the fight with Mayweather which is a long time coming. If they can win their next fights, it's definitely the fight that has to be made but there's no guarantee that they will win their next fights especially in the case of Mosley. I'm not saying Pacquiao will beat Mosley if they fought or vice versa but based on the question which you asked- "who has the better resume?"- I think you would have to go with Pacquiao.