The first thing you should consider is the price, as some are more expensive than others. Personally, I took the IELTS Academic because I felt like it is the most recognised one and because it isn't level based, so if you do really well you can probably reach a higher band score than the minimum level required by the university.
I strongly recommend academic ILETS UKVI as it a bit cheaper than the traditional academic and it is approved by UKVI.
Also I would recommend to take the exam at one of the British Council centres. They have great material online that you can train yourself on and get the required band score in all skills.