I recently purchased the CBFM but am wondering if I should return it and get a CUE II instead. I will be ttc a girl using O+12. Which is better for this purpose or are they both about the same since I will still have to monitor CM and cervix changes to pinpoint O+12 anyway.

Thanks!

 Yes you will still have to monitor your CP and CM to pinpoint O+12.  If you have already put your money into the CBEFM then I would say keep it.  These monitors can get expensive and if you are just watching for a CM change then you don't need both of them.