I think is over-rated. While you often will get NNN leases, the downside of managing tenants (non compete clauses, expansion, TIs, percent rent) is harder than office. Also, retail at least right now is at really low cap rates- very hard to get a decent spread off the lending rate. The biggest retailers (Lowes, Nordstroms etc) get outrageous lease terms- I call them the big box bullies. you'll pay dearly for them to anchor your mall, and if you end up with a small strip center, you may end up negotiating percent rent and other concessions. Also, mall and strip design goes out of style faster than office does- you'll end up renovating more often. None of which you have to do with the other asset classes such as office, industrial, self storage.

As an investment, multi tenant office and medical office offer much higher cap rates. You can sometimes get single credit-tenant (S&P BBB+ or better) offices with 10+ years on a NNN lease (government, large corps). I just saw one yesterday with SSA (social security admin) on a 10 year lease. full service of course, but a sold tenant