Benefits of 401(k) over Property?

[Brianna H.]

My husband's and my goal is to eventually use rental income as our retirement income. We currently have one rental home and are looking to have ~10 within the next 20 years. 

So the question is...what is the benefit of putting our money in a 401(k) over saving money for our next rental home? Obviously the 401(k) is sheltered from taxes until we are 59 1/2 (30 more years), but are there other benefits that I am not taking into account?