The best thing about folding bicycles is that they can be broken down into a more compact size. You can fit the bikes into a car or train easily.
The bad thing about them are that they cannot cycle fast as well as Cross bikes or Road bikes. They are more expensive than Cross bikes as well. They usually cost more than 100,000 yen at a minimum.
I believe that my folding bike is well worth the cost and have traveled a lot with it.