Riverside vs Wadsworth Complete editions

There seems to be a stark price difference between the two versions.

-Riverside Complete 2nd edition

- Wadsworth Complete 2nd edition


The Riverside edition links to a 'newer' version (The Wadsworth edition), with a higher price tag, additional authors, but the same publish date of December '96

Both have the same primary editor, G. Blakemore Evans, but the latter has a higher price tag and additional authors.

Can anyone enlighten me upon the differences?

Thanks!

I've also been trying to work out the difference (due to the Wadsworth edition being more readily available in the UK).

I posted about it on the Shakespeare reddit here.

Have you had any luck finding out the difference since your post?