This is what I have in my notes. I think it was B747-437B who originally suggested this on another thread:

If you are a fan of aisle seats, make sure you get a "G" seat on either 777 or 744. Those are the only aisles that are guaranteed not to have the annoying Krisworld entertainment box blocking your legroom.
Row 49 is the way to go on ALL the SQ 744s. It is not only an exit row with extra legroom, but more importantly it has no bulkheads in the center section to house loud babies.

From AirlineQuality.com:

Aircraft : Boeing 747-400 Seats : BC and JK - row 49
It's the exit seat near the galley but there's no toilet and the SQ staff is very quiet so you won't be disturbed. Lots of leg space and you have your personal screen even more adjustable to your needs as it is not in the seat in front of you but attached to your own seat.