Apple says that Touch ID's false positive rate is about 1 in 50,000: https://support.apple.com/en-us/HT204587
This number was also mentioned during the presentation today when they were comparing the two.
It was stated in the keynote that the numbers are much better (an order of magnitude) for face versus fingerprint.
In the keynote they've said that for Touch ID the error ratio was significantly lower, 1:50,000 to be exact.
Source? I was under the impression that fingerprint recognition was more secure than facial recognition.