No personal experience. But if it's between the two:
In terms of writing speeds for DVDs, the only difference between the 2 models is for DVD+RW, the Pioneer rewrites at 2.4x, and the Sony at 4x.
For CD writing, the Pioneer for CDR and CDRW is 16x/10x, while the Sony is 24x/16x.
The Sony has higher specs.
I read a review in a magazine (in Chinese I'm afraid) last week which covers all the current dual DVD writers. According to that report, at the same writing speed, the Pioneer writes faster than the Sony (but of course the Sony will still be faster writing a DVD+RW at 4x than the Pioneer at 2.4x).
But more significantly, perhaps, the DVDs (both + and -) written by the Pioneer has better compatibility with home DVD players than the Sony.
A review of the Pioneer on CDRinfo click here does confirm that the DVD videos written by the Pioneer do have good compatibility. That review also shows that at the same writing speeds, the Pioneer is faster than the Sony's predecessor (not the current Sony model).
This review click here shows the Pioneer writing movies faster than the Sony, but much slower than the Sony in writing and reading data.
click here for users' views
These reviews are not always reliable, and sometimes they conflict, but overall, it seems the Pioneer may have a slight edge in burning movies (if that's the main use), if your friend doesn't mind having to burn DVD+RW at 2.4x only.