Classic does have higher player count than Era most of the time, but Era players are much more active in their forum (they notify u to register) and well made contents.
I didn't play Era that much, but I never experienced 'server lag' in Era. Probably because Era has very spread amount of players on the map, versus classic 70% of players are in Graal city or inside the Battle Arena. I think Classic and Era won't die for next 10 years, unless there is like 'rape scene' happens and graal is involved in and bs judge force a game to shut down like ameba pico world.