No vb mobile theme exists for vb3. I do have a light theme available but its not used much. I uninstalled tapatalk last year due to privacy and security violations. Which was a very good decision. But yeah the choice to move to xenforo for vbulletin webmasters will depend highly on how mobile ready xf2 is.
If xenforo wants to accelerate its marketshare growth then it needs to rigorously overhaul mobile functionality because the platform that adds the most compelling mobile experience will pull a lot of websites towards it. We need push, camera upload, location services, better editing, better mobile navigation, messenger, instant content updates, add friends to mobile contacts and message contacts through xenforo, use mobile payment services for account upgrades and more, etc, etc.
Its quite a challenge. But imagine what addon developers would create once they get access to all that...
250K+ users per month with great looking responsive theme, I've seen a 99.9% reduction in complaints about tapatalk since I removed tapatalk. Is their a spanish inquisition app? that's probably the only thing that could be more painful than tapatalk.