This is a great conversation and something I frequently ponder. I will say, in the end for me, I also like the diversification. You can only put a max 17,5k into your 401 each year (at least for me at particular income level via regulations) and so I don't mind putting that 17 into the 401 and then focus other monies on real estate and other investment opportunities. I, too, don't like to have all my eggs in one basket.
I will say that this weekend I was looked at my past year 401k data and it stated I had a 1% return. However that was on the total money compared to last year. At first I thought that was terrible, but when I separated out how much of that came from "free money" by employee matching, that is a much higher return, in the mid 20%.
So I do think that if you have the means to put that 17 into 401 and it not affect what else you are doing, gets you free money via employee match and allows more diversification, I think it's a good thing.
Given medicine is my profession and not finances, this is all simply my humble opinion.