1, safety of the $$$- the higher the rate of the return, the risk also higher, ex: stock= you put the all the eggs in one basket, company doing well, you do well also, if company go broke, you too. MF= you put the eggs into hundreds diff companies share in one MF share, risk is low, so as rate of return, but safer, long term to gain the profit where stock can be buy and sellweekly. 2, Time= to double your $$$, the early you start, the better and more doubled by the Rule of72. The Tax benefit=Tax now, The tax later[deferred],IRA,401K,403,SEPetc.. 3, The tax never [will tell you later.] 4, Inflation= We cannot do anything about this, except $$ must put the account where the rate must be higher than the rate of inflation. One last thing, I like to mention, young people has enough time to recover, but old people no enough time to recover, therefor better to put the money where low return with low risk. If you know where they pay high rate of return and low risk, let me know!