There are many popular exams and the exam you should take depends purely on your objectives. Whether you are going to university or just looking to work in the UK, we are going to discuss two popular options you can choose from.
For academic purposes, the IELTS can be considered one of the most important exams when applying to university worldwide, especially in the UK. The university will require you to pass an IELTS Academic exam, unless you are a national of an English speaking country (United Kingdom, United States, Australia etc.) You will also need to pass with a satisfactory score, which will depend on the course you choose and also on your university. You should always check the entry requirements of your course. For example, in my case, I had to pass my IELTS exam with at least 7.5 as I was going to study History. Essay-based subjects generally require a higher level of English, while science-based subjects are more lenient and usually accept at least a 7. As you can notice, you receive a score in the form of a scale. This is from 0 to 9 and each score corresponds to a CEFR Level. This is by far the easiest way to display your level of English to an academic institution, which is why this test is recognised by most universities. The downside of IELTS is that it can be quite expensive. An IELTS Academic and General Training exam costs between £162-£180 depending on location. In my experience as a student, that was a good investment in the long-run due to the fact that I needed it for university, but it is definitely a financial commitment for a student.
However, if you aren’t moving to the UK for academic purposes and you’re just looking for a job in the UK, a more useful exam would be one of the Cambridge English: Business Certificates (BEC) suites of exams, for example the C1 Business Higher. These exams are made specifically for professionals. While displaying your level your English on the CEFR like the IELTS does, what it also does is ensuring employers that you have the right level to function in the workplace environment and that you know specialist terminology. This is more appropriate if you have already finished university and are looking for a job, because it can prove that you will easily adapt to the English terms used in an office.
This image shows how each exam compares to each other in terms of level. For example, if you take the IELTS Academic and pass it with a score of 7.0, you get the same CEFR Level as if you pass the C1 Business Higher with 190. However, you would demonstrate different specialised knowledge. In terms of the IELTS Academic, you would prove you are capable of understanding academic language and lecture presentations extensively used at university, whereas through the C1 Business Higher you would demonstrate an extensive knowledge of business language needed for an office environment, for example.
Depending on your circumstances, you should be able to choose the exam that is best for you. Good luck!