IELTS and OET differ in several categories – we list a few here:

1. Context
The main difference is the context within which each test is taken. The IELTS test will test your English within the context of a wide variety of topics. The OET will test your ability within the context of your medical profession. Therefore, if you are a nurse or a doctor, you will be tested on things related to your job.
2. Cost & Availability
IELTS is much cheaper than OET and is available in more places. OET costs about three times more than IELTS.  There are also more IELTS test dates available than OET. Anecdotal evidence suggests healthcare professionals are more likely to pass OET as the language used within the exam reflects their occupation, therefore whilst the OET is much more expensive, candidates may only need to undertake the test fewer times to pass. In some countries, such as Ghana, there isn’t an OET Exam Centre – so it isn’t available for Ghana nationals to take the OET in their own country. This is true of other countries too.
3. Preparation
They are both English language tests, so a good level of general English is required, but there are also key differences in ‘test skills’. Therefore, the preparation for each test will be different.
You will have to invest a significant amount of time and effort into preparing for each of them. If you have already invested a large amount of time in one, it may be a bad idea to throw that away and switch to the other.
There are also 3 million IELTS test takers every year and only 25,000 OET takers. This means that there are far more preparation options for IELTS, ranging from a huge number of free options to online courses and private tuition. The range for OET is rather limited.
4. Acceptance
IELTS is viewed as the ‘gold standard’ and is accepted everywhere. OET is accepted by a smaller number of bodies and institutions. IELTS may be a better choice if you are unsure of where you might work or study in the future.
5. Re-taking the test
One of the most frustrating things about IELTS is that if you fail one of the four skills, you have to take all four again. This is very disappointing for students who struggle with any one section.
An OET candidate can ‘bank’ the higher scores and focus only on the skills they ‘failed’. For many candidates, this is the biggest benefit of OET and one that IELTS should consider introducing.
6. Validity
In the UK, OET and IELTS are regarded equally as valid English Language certificates. As long as you obtain Level 7 in IELTS and Level B in OET for each of the skills areas. Please note: IELTS Level 6.5 is acceptable for the Writing Skills exam.