With 4.1.2, vbulletin have put in their own detection script - I suggest as a start you disable your previous one.
The vBulletin Mobile Style is written for webkit based browsers, so will work on iPhones and Android based phones, but may not display well on other devices.
This style should work for pretty much all devices. As for which one is better, that's subjective - they would both have their positives and negatives.
As a start, you could install this one
and also use vBulletins Mobile style and configure the vBulletin mobile detect options in Style & Language Settings to use vBulletin's Mobile style for 'Modern Browsers' and this one for 'Old Mobile Browsers' - although personally I'd configure them both to use this style

Best bet is to get your users feedback and see what they like