Well, i see many have been saying Vbulletin died with vb 5.x. I really don't know what sort of illusion is this and what is your aim trying to portray this, seeing that vb 4.x is great and way better than Xenforo.
Others are jumping off the boat, because of this entire Xenforo vs IB saga, but honestly, you forget one thing, it is us customers who buy your addon. I've seen many of the coders who have moved to Xenforo, kept encouraging their vb customers to migrate to Xenforo in order to sell their addon there.
You might not like the subject because it is touching your $$ but it is true that you've decided to abandon vb customers and those who gave you fame in the first place.
Many don't like the way IB runs thing and how VB do not listen to many of the requested features, but that doesn't mean the product is bad because vb 4.x is great, vb 5.x needs at least 2 years of development, it is currently in beta stage, never gold yet in my own eyes.
If i am going to compare vb 4.x with Xenforo, definitely vb 4.x wins in term of features and stability.
If i am going to compare vb 5.x with Xenforo, XF wins over because it is much more faster, Seo friendly and easy to use but not feature rich. Xenforo doesn't even have basic profile gallery, let alone they are using an Editor
http://imperavi.com/redactor/, that isn't as nice as the CKeditor
http://ckeditor.com/demo#standard