From the guys standpoint:
I don't notice the shrinkage
Briefs keep you warmer, but I prefer boxers (more breathing room)
I can feel a difference when I enter her throat, the muscles contract and try to force it down "milking" it.
never had my prostate rubbed
and it feels wonderful.

Course, I'm sure it's different for every guy and you'd still want to experience for yourself.

__________________
"BOY: On a hot summer night, would you offer your throat to the wolf with the red roses? GIRL: Will he offer me his mouth? BOY: Yes. GIRL: Will he offer me his teeth? BOY: Yes. GIRL: Will he offer me his jaws? BOY: Yes. GIRL: Will he offer me his hunger? BOY: Yes. GIRL: Again, will he offer me his hunger? BOY: Yes! GIRL: Yes. BOY: On a hot summer night, would you offer your throat to the wolf with the red roses? GIRL: Yes. BOY: I bet you say that to all the boys!" -Meatloaf