What is the difference between a 6 wheel swerve and a 4 wheel swerve?

[AdamHeard]

Originally Posted by Dillon Carey

well...one has 4 wheels and the other has 6.

The main reason for 6 wheels is to gain the ability to operate in a similar fashion to a 6 wheel tank drive, while still being able to swerve.

I keep seeing this posted, but I don't understand how that is an advantage.

What is a 6wd doing that a swerve can't (aside from possibly climb easier, which wasn't the reason posted in the document...)?