Here's the really short guide to life insurance: http://www.reddit.com/r/personalfinance/wiki/insurance
Plus there are the tax and loan benefits of WL. They are inferior with 401k and IRA plans. You can't take out a loan whenever you want. You can only take out a certain amount (usually up to 50%) and only under very strict circumstances. There are maximum contributions with 401k. No so with WL. 401k's are taxed as ordinary income. There are more fees over the longer run with 401ks (2-3% every year vs just high front load with WL). You can't withdraw before 59.5 without penalties (except for 72t). There are strict provisions on when you have to pay the loan back.
With WL you can take out your money whenever you want with no penalties. You can take out loans whenever you want and pay them back whenever you want or just not pay them back at all. Most smart people will just take out loans against their policy and effectively access their money tax free. You can't get that with 401k and IRAs.
Taking out loans against whole life policies isn't something I was aware of though. I'd be interested to know what type of rates you could get with the loans against that compared to home equity loans or equity lines of credit that you can also use to get at the money you put into paying off the mortgage if you need it.