With company matches, a 401K is free money, even if it takes a couple years to be fully vested. Example: previous employer matched half my contribution up to my 8% of salary. That's 4%, a 50% return right off the bat. Sound investment options magnify that proportionally.
I worked 17 years, give or take a couple months, so vesting my 401k was a given and went with me fom my first employer to the second.