The pros & cons of these 2 cameras have been extensively discussed by other posters. I'll just add one comment.
Not knowing what drew you to a choice between these two, I'll suggest that you explore the new Zeiss Ikon & its ZM lenses. If it's the Zeiss lenses that attracted you to the Contax G2, they are now available in M-mount to use on the Bessa R3A, the new Zeiss Ikon, or any other M-mount camera. Early reports indicate that the lenses are at least as good as the Contax G versions - if not better. Information is available at www.zeissikon.com.