Moving from Vbulletin 4.2

I decided to change our forum script to another forum script. But I can't decide. Which is better? IPB or Xenforo?

Currently we have 46k topics, 884k messages and 112k users. We don't want to alianete our users. We are looking for:

1- It must be good on SEO.
2- It must have a good support, themes and add-ons.
3- It must be user friendly.

In terms of these three, which one is better? IPB or Xenforo?

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