74A business main deck or upper deck
 

which one is better?

i prefer the upper deck, which is much quieter

Is it me or the upper deck is less comfortable and a bit less width than the lower decks? I've tried the one in 74A (upper deck) and 77A and finds the 77A to be a little wider...

Upper deck seats have more head space when in bed mode. This is from where the side storage bins used to be.

Upper Deck hands down! ^

The upper deck seats are longer than the J seats in the main deck, and the upper deck is usually very quiet and has good service, but the front lavatory for crew use only.

+1, and more attention from the FAs

Agree!!! my last flight from DPS, ISM+SP+FP+FA total 4 cabin crew in upper deck.

Lower deck for me. I'm 6 foot and carrying a few extra pounds, and found the upper deck too small and claustrophobic (although I like it in the BA layout). Think it is a very personal call.

Are the business class lavatories the same size on the upper and lower decks?

Same size; fyi, 3 lavatories : 24 pax in main deck and 2 lavatories : 22 pax in upper deck.

Unfortunately, I'm running 0-4 on upper deck J service so far. And, this is on multiple airlines, btw: UA(1), SQ(1), and CX(2). All of these have been mediocre compared to the J service on lower deck or single-deck aircraft of the respective airlines.