Could someone who knows about these things, compare Z3 with the Google or-tools? (https://code.google.com/p/or-tools/ https://code.google.com/p/or-tools/) Pro

Could someone who knows about these things, compare Z3 with the Google or-tools? (https://code.google.com/p/or-tools/ https://code.google.com/p/or-tools/) Pro's/Con's of the two?