i think it depends on school or company's policy. there is nothing we can tell.

my ld's school helped him get labor certificate, and he prepared I-140 and I485 by himself. We got GC in one and half year.

But I was told that our school does not support GC application for other position besides faculty. So I guess if position is on research track, you probally have to apply for GC through NIW, etc.