The difference is almost all big law firms pay first year associates the same amount (within the same city, at least). For the last few years this has been ~160

The difference is almost all big law firms pay first year associates the same amount (within the same city, at least). For the last few years this has been ~160K in NYC/DC/SF. Smaller firms typically pay much, much less. Getting into big law has little to do with prior experience. It's much more correlated with law school, but I know people who went to second rate schools who got offers to prestigious big law firms. I believe about 25% of employed new graduates go into big law.