Sorry, the information I reported about the resolution of iPhone 14 was inaccurate. Upon checking other articles, it seems 14 has the same front camera resolution as the other TrueDepth-enabled iPhones, (version X and higher).
Potential facial mocap advantages of iPhone 14 include: the A16 Bionic chip. Probably provides faster processing and improved battery usage and longer battery charge life from a charge, as well as less overheating during longer Live Link Face recordings. Apple.com chat technician indicated: iPhone 14 has battery life of upto 20 hours compared to 17 for iPhone 13 mini and 15 for the iPhone 12 mini
Other features that might be advantageous:
An extra GPU core (5 total, rather than 4). Maybe that helps with drawing Live Link Face’s wireframes.
Autofocus: 30cm to 150cm distance.
Larger maximum fstop might offer some improvement.
Here’s a comparison ‘straight from the apple’s mouth’ between 3 different iPhone models. iPhone 14 Pro vs iPhone 13 mini vs iPhone 12 mini - Apple. You can use that page to compare other iPhone models.
In terms of iPhone 14’s advancements for face mocap with unreal, the new features seem evolutionary, rather than revolutionary… but if you are ready to upgrade, you might gain something from the new features. If you’re on the fence, it might be worth heading to the Apple store to do a comparison.