The decision this compares
This is about extra money beyond your everyday budget and emergency fund: should it go into superannuation (on top of what your employer already contributes), or into a personal investment portfolio such as ASX-listed ETFs? Both can hold similar underlying assets. The real differences are tax treatment, access, and flexibility, not the investments themselves.
Tax treatment
Extra contributions into super can go in two ways. Concessional (pre-tax) contributions, such as salary sacrifice, are taxed at 15% going in rather than your marginal rate, up to the $32,500 annual concessional cap (which includes your employer's SGC). Earnings inside super are taxed at up to 15% in the accumulation phase and 0% once you start a retirement income stream. A personal ETF portfolio is funded with after-tax money. Dividends and distributions are taxed at your marginal rate each year, though franking credits reduce or eliminate double taxation on Australian shares, and capital gains held over 12 months get a 50% CGT discount when sold.
Access and flexibility
Superannuation is locked away until you meet a condition of release, generally reaching your preservation age and retiring, with limited exceptions such as the First Home Super Saver Scheme. A personal ETF portfolio has no such restriction: you can sell and access the money at any time, for any reason, though selling may trigger CGT. This makes ETF investing the more flexible option for goals that might land before retirement, such as a house deposit or a career change.
Contribution limits
Super caps how much concessional and non-concessional money you can add each year (see the Voluntary Super Contributions guide for the current limits and what happens if you exceed them). Personal investing outside super has no equivalent annual cap, you can invest as much as you have available.
A rough comparison
Consider $10,000 a year of extra money over 20 years at a 7% return, a common long-term assumption for a diversified portfolio. Directed into super via salary sacrifice by someone on the 30% marginal rate, the 15% contributions tax means more of each dollar starts working immediately, and earnings are taxed more lightly along the way. Directed into a personal ETF portfolio instead, less of each dollar survives the initial income tax, but the money remains accessible the entire time and isn't tied to a preservation age decades away. Use the Superannuation Calculator and the ETF Growth Calculator with your own numbers to compare the two paths directly.
What tends to matter most
The time horizon until you can access the money is usually the deciding factor. Extra super contributions tend to suit money you genuinely will not need before retirement, where the tax advantage compounds over decades. Personal investing tends to suit medium-term goals, or simply a preference for keeping money accessible. Many people split extra savings between both rather than choosing exclusively. This is general information, not a recommendation, your own tax rate, timeframe, and goals will change which balance makes sense for you.