Interesting question – let’s start by saying that regardless of whether you take the test on a computer or with a pencil and paper the test format, the question types, the time allocated to each test part and the content are the same. And because the content for both the IELTS on paper and IELTS on computer test is the same, the level of difficulty is also same. The marking system - the way your answers are assessed and graded is exactly the same. Also, regardless of which you choose, the speaking test will be the same – it is a F2F interview with an IELTS examiner. So, it is a myth that one is easier or more difficult than the other.
What is different is your test day experience. If you take the ‘paper’ test you write your answers to the L, R & W parts onto the answer sheets with a pencil – you can use a pen for the writing if you prefer. If you choose to take the computer test than the L, R & W parts are completed on a computer by typing the answers onto the screen – but you do get a pencil and sheet of paper to write notes for the listening test.
So, here is the first decision point – how neat is your handwriting? If it’s poor (mine is hopelessly poor – I can’t even read it myself) then like me you should consider taking the computer test – the examiner is not going to spend time trying to decipher (de-code) your handwriting. The opposite side of this question is – how good are your keyboard skills? If you are not ‘tech savvy’ then you should consider the paper test.
The second point is this – you get the results faster if you take the computer test. The official line from Cambridge and IDP is that it takes 3 – 5 days to receive your results for the computer test (although in some places it is even quicker). In contrast, it can take up to 2 weeks before you receive your results for the paper test. If this is important to you then opt for IELTS on computer. On a similar note, in many test locations there are often more available dates on which to take the test on computer, so that might also be a factor.
Overall, the main deciding factor is personal preference. Are you more comfortable sitting at a desk with a pencil and paper, writing your answers onto an answer sheet OR are you more comfortable in front of a computer, typing answers onto a screen? Answer that question for yourself and you then know which you should take.