The 250cc lites class is set up to give A Riders a chance to show their stuff while earning points to race Supercross in the future. You will also see Pro Riders here once in a while trying to make a name for themselves and get noticed by doing well so they can move up in the ranks.
AX Class is considered the premier class were you will see Top Pro's for all over the world compete on 450cc bikes in hopes of becoming the next AX Champion helping them earn their way up the ladder and maybe on to a big contract Supercross deal.