Grammarly is more preferred by many English writers because it does not require you to download any software. Its grammar checker works directly online. You just go to their website and type / copy your text into the white space and check it for correctness / quality.
We have tried Grammarly's software for you and here is a little bit of what it does:
Grammarly has more than 3 million registered users and is used by more than 100 educational and corporate clients, including Princeton University, University of South Florida, University of Virginia, and many others. Grammarly makes a meaningful impact in users’ lives; students get better grades, professionals accelerate their career progress, and language learners improve their written English.
College Students Praise Grammarly
Grammarly surveyed its thousands of college student users and were excited to learn that: 99% of students report Grammarly having improved their writing grades!
Overall: We think that it's worth trying and there isn't much to lose since you can cancel your subscription within 7 days and get full refund.
This one is preferred by some users because you only pay once and the software is yours for lifetime with its good and bad. Once you download it, you run the program, type in your text and the program corrects your mistakes. It will also work automatically when you are typing in Word, PowerPoint, etc. It's got an error explanation tool that helps you learn from your mistakes. There are both good and bad reviews about WhiteSmoke on the internet regarding what the software can do. Again you can see for yourself by at least downloading the free version.