I use both on my phone but I have heard of the fingerprint scan allows some people to gain access because of faulty systems in phones. I also have a scanner on my laptop but I do not use it. I would rather just use a login password for that.
I feel safer using both rather than one or the other but I think it may be easier to crack a pin than it is to actually crack a finger print scan.
Honestly the effectiveness of either method depends on proper implementation, management, and user awareness. Both have their strengths and weaknesses. Pins can obviously be cracked easier than a finger print. It is very unlikely someone trying to access your data with have the same finger print as you or know someone that matches your own. I use both too.
When they work, yes but I think it is always best to use both in the event one fails. I think people rely too much on one or the other and never bother with having both as an option.