my 2 cents, we regularly travel with our now 21 month old.
the answer really depends on the age of your baby and what they are like.

If they are quite active and not much of a napper then definitely go the sky couch and definitely get 2 if you can. For a baby and 2 adults if you can't buy 2 couches then at least get a skycouch and the isle seat across. (1 sky couch not enough for 2 adults and baby if you want to sleep!). Also they will not let you have all three seats converted with 2 adults and a toddler (probably same with baby).

If they are a "good" sleeper then go with the 2 x PE seats especially because its a night flight and put them in the bassinet. Our baby NEVER slept in the basinet, the NZ one is not very high and she always kept popping her head up.

If its a day flight we found skycouch awesome because lots of room for them to play (we normally get one skycouch and an isle seat).

If you are traveling with a child then sitting and enjoy a PE and even J meal is not possible (at least we never have) normally we get the express option and try get as much rest as possible.

The most ideal situation for us has been 2 x NZ J seats for night flights. She tucks up next to one of us and sleeps the whole way. Also we leave the seat in "bed" mode and she has a lot of room to play. You can also utilize the ottoman of your partner.

We tried PE once and never again! The biggest issue is not being able to lift the arm rests up so unless you buy them a seat you are very restricted.

Also: in my opinion sleep for the adults is a bonus! The aim is to have a happy sleeping baby! As long as they are comfortable I don't care how much sleep I do or don't get so this is why I don't mind the sky couch.

**long the days of my noise cancelling headphones and baby/toddler free flying!