@Doug Phillips, a couple things come to mind. I own a small company and we offer a 401K to employees through Betterment.
Our plan is a "Safe Harbor" plan which just means it's not very customizable. We match 100% up to 4% gross income. Safe Harbor plans are out-of-the-box in an effort to keep setup costs to a minimum. They're great for a small company like our because it makes it super cheap to start offering a 401K benefit.
The thing about Safe Harbor plans is they vest immediately, and the employer MUST contribute the set amount. So even if an employee doesn't contribute, my company must still contribute 4% of their gross salary and it vests immediately (literally free money).
So ask if it's a Safe Harbor plan, and if so, clarify this point. If you're getting 4% free and clear you may decide not to contribute at all if you're looking to invest in real estate instead. After 4 years of maxing my 401K out I've just stopped contributing to do just that.
Secondly, review (or ask HR) If the plan allows you to loan against your balance. Ours did not but I've just amended it so that we can. If you can loan against your 401K you'll be able to loan 50% of the total vested balance or $50k (whichever is less). The loan must be paid back via your paycheck (with a small interest rate paid to yourself) over 5 years unless you are using the money for a primary residence in which it can be paid back over 15 years.
There are two catches:
1) You can't make extra payments on the loan without paying it off in full
2) If you leave your employer the loan must be paid back in full immediately (I'm not sure exactly how long, but it's quick).
I'm outlining this because there's a clear benefit to investing in a 401K since it's pre-tax money. While I was contributing the maximum (~$1,500/mo), I'll be lucky to see $1,000 of that as net pay (obviously this depends on your tax bracket).
So you need to ask yourself a couple questions like, is it best to contribute the maximum to leverage pre-tax savings and then loan on that amount down the line? Is the money instead more valuable to you now to be used for real estate acquisitions?
It all depends on your personal goals. And some of the things I mentioned above could change the answers to those questions, especially the Safe Harbor one.
The way my wife and I see things right now, our main objective is purchasing cash flow properties to reach financial freedom. Contributing to my 401K doesn't align with that goal even though the pre-tax savings is significant. The fact that I still get the 4% company contribution is nice. If I didn't I'd likely contribute up to whatever the company would match (in my case 4%).
I am not a financial adviser, so please take everything I say with a grain of salt and do your own due diligence.
Best of luck!