First, you have to consider that each maker of fingerprint sensor uses a different technology for creating a fingerprint template (a representation created from a image captured by the fingerprint sensor) and matching the template against a reference template (created during the enrollment, when you register your finger).
In terms of technology, to compare the how secure are these different ways to authenticate a fingerprint, there are 2 main parameters:
- rate of false negatives: the percentage of times a finger that should match the reference finger template fails to do so (this will be the rate of 'annoyance': the chance the sensor will not allow a legitimate user to login)
- rate of false positives: the percentage of times a finger that should NOT match the reference finger template will actually match (this will be the rate of security failures: it means there is a potential for another finger to be seen as the correct finger)
However, most security problems in consumer fingerprint authentication products will actually not be in the technology itself, but in the implementation. E.g. not properly protecting the passwords that are stored behind the fingerprint authentication, so the attacker can ignore the biometrics and grab them directly, etc.
I would want to see the specific details of how the system is implemented before deciding and I would say that unless system security was a key requirement during the whole design I would not feel confident.
I think this is similar to the encrypted USB keys... most of the 'secure' consumer disks have almost null security and only the expensive ones, usually the ones designed for security (i.e. Ironkey, etc) really provide protection.
Not sure if this answers your question, hope this helps.