According to the Baseball-Reference HR log:
Pujols, with 266 career HRs, has hit 32 to right and 13 to right-center.
Vlad, with 351 career HRs, has hit 41 to right and 24 to right-center.
Manny, with 481 career HRs, has hit 87 to right and 25 to right-center.
A-Rod, with 491 career HRs*, has hit 77 to right and 47 to right-center.
Sosa, with 601 career HRs, has hit 89 to right and 46 to right-center.
Percentage-wise, that would be:
Pujols - 16.9%
Vlad - 18.5%
Manny - 23.2%
A-Rod - 25.2%
Sosa - 22.5%
Thus, my vote goes to A-Rod.
* entering Saturday