I ignore everyone else, cos they're either teeny weeny people or on directionals... I've been on on a 17 when others were riding 7s and still had fun. Also there are people here who truly believe that anything more than a 14 is just "too big" for them
and won't even try a bigger kite, no matter how light the wind is.
That said... the more wind there is, the closer the kites sizes get. I can get away with a 10 when other TT riders are on 9s or 10s too... sometimes, anyway!
The lighter the wind, the more kite I need. It's an exponential thing
it's why I always take 2 boards over to the beach too.