I just checked my two trips this summer: three of four trans-Atlantic segments are on the 747, so I'll be able to directly compare the WBC in the 747 and 330.
I have 77J on the 747 outbound and 2B on the 330 return for the first trip. Too early to select seats for the next trip, but I'll probably do row 77 in the upper deck both ways, if available.

I've been on the upper deck on KLM and United, but I can't remember if I've ever flown the 747 with NW.