I do both. @Account Closed
401K
My company matches 100% up to a 6% contribution, and then gives an additional 3%. I get 15% for really only coming out of pocket for 6%...thats pretty damn good for now. I put those funds into accounts that guarantee a small return of 8% per year plus some growth from the funds based on market conditions. This will build for a while until I decide to stop working and then plow it into notes or something through a SDIRA.
Real Estate
I own 4 properties that are used for short term rentals right now and I re invest EVERY dollar back into mortgage pay down. In 5 years I will own everything 100% outright and then I will cash flow for a while. I will 1031 exchange into multifamily units after that point.
What I am saying is both are 100% feasible. Having only one does expose you to more risk for not having enough to retire on later in life. Its the same concept as the benefit of investing in multifamily over single family...spreading the risk..
There is a really damn good BP podcast with a guy who talks about universal indexed life insurance and things I believe it was episode 017 with Jeff Brown.