Five reasons to use vB5 instead of vB4

[Mark.B]

If you are happy with your site then I would suggest you stay with what makes you happy.

But VB5 does have its benefits-

1) Responsive Design
2) Site Builder
3) Stronger Passwords
4) Option to require paid subscription to register
5) Updated ckeditor

Bonus #6 - Some people like the style better.

And since then:

User mentions
vBulletin Messenger
Event content types
(Indeed proper content types are themselves a good option)
Built in selection of styles rather than just one
Easy access to additional.css via front end site builder
CKEditor updated again

I'll probably think of more.