Many factors come into play, such as what fight, what prog point, what server/data centre, etc.

I'm a player on Chaos, I have to go to Light to do any sort of raiding.
It was one of those self-fulfilling prophecies where everyone exoduses to another DC to get a party.

I find it amusing when my entire party is from Chaos.

I hope we get a cross-DC PF in the future, even though it's been said it could be years.
Honestly, unpopular an opinion as it may be, locking DC travel completely would also "liven" up home data centres for many.