www9.plala.or.jp is a 4 character word. It is a excellent domain length for people to type quickly.
Hyphens and Numbers
Hyphens and numbers in a domain name is likely cause loss of visitors to the website due to typos and miscommunication. Try to avoid them unless the reason is something sensible.
Top Level Domain
www9.plala.or.jp is still good but not best as same as .com. This is designed to target a specific country or audience. Remember that you can lose some web traffic to .com version of the domain because people tend to type .com more than any TLD.
www9 is not a dictionary word but it contains dictionary words. Dictionary is most important to people because they will remember better without dictionary words. This domain is contained with www