Is the beaufort cipher just as secure as the Vigenere cipher?
Yes, it is.  The Beaufort cipher is identical to the Vigenère cipher except that, in effect, the plaintext alphabet is reversed (i.e. mapped A &rarr; Z, B &rarr; Y, etc.) before encryption (and after decryption).  The reversal adds no appreciable security, but it also cannot make the cipher less secure.