Well the 939 3200+ has more pins (obviously
) which increases data transfer so between those two it should be relatively equal if not the socket 939 coming out a little on top. Don't forget though with the Socket 939 you will have dual channel capabilities available to you so that will aid in speed.
If you wanted to go socket 754 you could consider getting a 64 3400+ Mobile, Low temps and excellent OC'ers just like the Mobile XP's of their times.
However, I'm checking up on those mobiles because I know there's DTR, 62w, and 35w mobiles, and the DTR may require a specific board. I'll get back to ya on that.