One module retake:  Only on computer delivered IELTS, you can retake a single module.

Get results in 3-5 days.

During Reading test, answers are auto transferred, no extra time wasted on transferring answers. 

You can see a clock on computer screen (a timer) for Listening, Reading and Writing. 

Can copy-paste answers during Reading test. 

Can highlight texts, make notes. 

 During writing, can easily erase, modify written sentences. There's also a word-count shown on computer screen. 

 For listening, and reading test, you can see which questions you have left un-answered on the bottom of the screen. 

Listening, Reading, Writing, Speaking - you have to take all 4 modules in one day.

There will be no grammar-check. We are used to having grammar checks in our computers, this habit could cause crucial errors. Though, all you have to do is revise for errors. 

If you are not skilled with computer then computer based test is not for you. You should have typing speed of at least 40 wpm (words per minute) if you are considering this. 

Do not choose this for the pros, you should only choose computer based exams if you are more comfortable typing in keyboards rather than writing with pencils.