Unicode is the universal character encoding, maintained by the Unicode Consortium.
This encoding standard provides the basis for processing, storage and interchange of text data in any language in all modern software and information technology protocols". Unicode covers all the characters for all the writing systems of the world, modern and ancient. It also includes technical symbols, punctuations, and many other characters used in writing text.
The Unicode Standard is intended to support the needs of all types of users, whether in business or academia, using mainstream or minority scripts.
Most of the SAP implementations are done on Unicode system as it support all kind of languages, which is good for a company to expend their business. Another things is Unicode system requires 70% more storage area and processing speed to run the system perfactly.
There are systems like XI, which can work only on Unicode so it is always advisible to go for unicode then to non-unicode.