I will be a better student in law school because of my job experience. I am more valuable as a 3.4 student with 4 years of full time employment than I would have been with a 3.7 and one summer internship.
Maybe, but not necessarily. To say so would conflate experience with potential. Do you win with experience? Definitely. Do you win with potential? Maybe not. Give the 3.7 applicant four years and you'll probably have an applicant with a 3.7 AND four years of work experience, just like you.
There's certainly something to be said for the way business schools do things - that is, having full time work experience be pretty much a prerequisite - but (rightly or wrongly), it isn't the way law schools do things.
Remember that GPA plays second fiddle to LSAT. In your hypo, your four years of work experience haven't enabled you to score better on the LSAT (which is the best individual predictor of first year law school performance we have, as imperfect as it is). Why work experience doesn't play a huge role in law school admissions is, I think, more complex than "adcomms are biased because of their own high GPAs."