First choice for me would be "nobody": A vacant middle seat is always appreciated in Economy Class.
When flying longhaul in Business Class I have no preference as long as the person next to me does not interfere with my privacy unwantedly.
Occasions in which I have had an intense chit-chat (or deeper discussions) onboard an airplane with a total stranger are very limited (this excludes anything less than 5 minutes of talk).
I recall one flight on a UAX CRJ OAK
which was completely filled with a discussion with my neighbour (was about vacation and flying)
Another flight that saw quite some discussion & story telling (again: vacation & flying) was on a LH
B744 in Business Class flying FRA
(different occasion than above) when my neighbour in the window seat was a frequent flyer, this time on his way to connect to a NZ
flight to AKL
On flights to PMI
, I rather regularly encounter some chit-chat with pax next to me, who most often are older (55+) travellers due to the fact that I (39y) ply this route mainly in winter.
Carpe diem ! Life is too short to waste your time ! Keep in mind, that today is the first day of the rest of your life !