Over the past few weeks, we’ve covered the investing basics:
why index funds beat active management, how diversification protects you, and why starting early matters more than perfect timing.
You don’t need to read another hundred blog posts before you start investing.
You already know enough to take action.
But I also know what happens next.
You open an investment platform, start browsing options, and suddenly you’re paralysed by questions you didn’t even know you had:
- “Wait… do I want an ETF or an index fund?”
- “What’s this hedging option?”
- “Do I invest a lump sum or spread it out?”
- “What on earth is FIF tax?”
These are the questions that stopped me in my tracks – not because they’re especially complicated, but because they make it feel like you need to understand everything perfectly before you can proceed.
You don’t.
So here’s what we’re doing next.
I’m answering the most common “I’m actually trying to do this now” questions in short, practical posts. Just enough to get you unstuck and moving forward.
Starting with this one:
“ETF vs index fund – which one should I choose?”
If you’ve been exploring investing after reading my posts, you’ve almost certainly come across both terms. And if you’re like most people, you’ve wondered which one you’re supposed to pick.
Here’s the truth that will save you hours of research:
For an evidence-based investor, the difference probably doesn’t matter.
If your goal is to invest in a low-fee, passive, broadly diversified fund that tracks the market – then ETFs and index funds are close enough that obsessing over the distinction is a poor use of your limited time and energy.
But I know you.
You’re a doctor.
You want to understand things properly before you commit.
So let’s use a medical analogy to clear things up.
The Blood Pressure Analogy
Think about checking a patient’s blood pressure.
Index fund: the spot check
Index fund: spot checking
An index fund tracks an index (which is just a way of grouping companies – for example by country, sector, or company size) and is priced once per day at the end of trading.
You can place your order at any time, but it won’t be processed until the end of the day, when the price of the fund is calculated – this is called the Net Asset Value (NAV).
Think of this like checking a patient’s blood pressure.
You request a non-urgent blood pressure check once a day. The nurse will get to it during their rounds.
That single reading gives you solid, reliable information. Over time, the trend is even more valuable.
You miss tiny fluctuations throughout the day – but for most patients, you don’t actually need them. It’s simple, effective, and low-cost.
ETF: continuous monitoring
An ETF can be traded like a stock throughout the day, so its price fluctuates minute-by-minute during market hours. You can buy or sell at any point and pay the price at that moment.
Because it’s traded like a stock, you need to involve a broker, which usually means paying a brokerage fee.
This is more like putting in an arterial line.
You get far more information throughout the day and can see the blood pressure at a precise moment. But not everyone can put in an art line, so you need extra people (which costs more), and for most patients this level of detail is overkill.
What actually matters
Both ETFs and index funds can invest in the exact same underlying assets.
If two funds are tracking the same index, they own the same companies in the same proportions. The difference isn’t what you’re investing in – it’s how and when you buy and sell.
Same patient. Same blood pressure. Two different ways of measuring it.
Broadly speaking:
Index funds
- Bought directly from the fund
- Priced once per day
- Usually no brokerage fees
- Minimum investments vary
ETFs
- Bought through a brokerage (like a stock)
- Priced continuously during market hours
- Small brokerage cost per transaction
- Often no minimum – you can buy a single unit
Why this doesn’t really matter for you
If you’re following evidence-based investing principles, you’re investing for the long term (10+ years).
You’re building wealth through consistent contributions and compound growth – not through perfectly timed trades.
Whether you buy at 10am or at market close makes no meaningful difference to your wealth in 2045.
That continuous pricing feature?
It’s useful for traders.
You are not a trader.
You are a doctor building long-term wealth alongside a demanding career and a full life.
A once-daily “reading” is more than sufficient. There’s no prize for watching the market all day.
Two things to check – whichever you choose
Whether you end up choosing an ETF or an index fund, there are two separate checks that matter more than the label itself:
- Is the fund passively managed or actively managed?
Some ETFs are actively managed, meaning a fund manager is selecting stocks rather than simply tracking an index. These typically come with higher fees and, as we’ve discussed previously, rarely outperform the market over the long term. - What is the fund’s tax structure?
In New Zealand, both ETFs and index funds can be structured in different ways for tax purposes (for example, PIE vs non-PIE). It’s the structure – not whether it’s called an ETF or an index fund – that determines how it’s taxed.
I’ll walk through NZ fund tax structures in a separate post.
The bottom line
If you’re following the evidence and choosing a low-fee, passive, diversified investing option, the difference between the ETF version and the index fund version doesn’t really matter.
Either one is good enough to get started – and getting started matters far more than getting this perfectly “right”.
Evidence-based investing is just one part of your overall financial picture.
If you’d like a structured, evidence-based approach to improving your financial wellbeing more broadly as a New Zealand doctor, you can learn more about my CPD-endorsed Financial Resuscitation course.
This post is for general information and education only. It is not personalised financial advice and does not take into account your individual circumstances.