Master of science cannot be fully coursework. So there will be some research. If coursework plus research, the main emphasis is coursework and a small research project. The research project will be carried out in addition to classes and will last usually last between 6 months to 1 year. This programme most ppl complete in 1 1/2 to 2 years. Think bachelor degree with final year project, but bigger scale.

Master by research has full emphasis on research. Like what I did, I only had 4 class requirements, 2 class for 2 semesters and that's all. The rest of it comes from research, and it's almost like a mini-phd. Probably 1/2 to 2/3 phd project level. You will spend a lot of time on your project and you would need some decent results/analysis to graduate. Some universities will require you to have a paper in publication as well. Most folks take at least 2 years, majority up to 3 years.

The difference between the two is what you plan to do with your masters. If you want a quick masters just to boost your CV to work in industry or goverment (e.g. pegawai sains etc), then masters by coursework will be good for you. However if your passion is research, then masters by research will prepare you well for PhD. Also especially if you plan to apply for Phd overseas. This is because in academia, publishing is the main highlight. Even if you didn't manage to publish a paper, at least you will have a strong research background to back you up.

The thing is, Malaysia is not well-recognised for its quality education, at Master level. While good universities overseas will accept coursework mixture masters from UK, Europe etc, they will think twice for Malaysia since they are unfamiliar with Malaysia. Plus some of these coursework masters in UK/Europe do manage to get their name into a paper since they are in a large lab and they can help out a bit in large projects so they can get their name in. That is not really quite the reality in Malaysia for a lot of master students by coursework.