The oppo was my first portable DAC/amp and the mojo the second. Although I appreciate the oppo's capabilities it never impressed me. The mojo on the other hand the first time I heard it stunned me. I would say that the mojo is in another league. Way more transparent than the oppo and more musical. The oppo, in comparison, puts a veil on the music and sounds cold. My Focal Elear, which scales pretty well, makes the difference even bigger.
I would happily switch my oppo to something that is way more portable, say the dragonfly red.
In terms of performance per dollar I think the mojo also wins. Big time.
Is the mojo perfect? No. I love classical music and mojo has left me wanting in that department especially with large orchestral recordings. Also, be sure to treat those USB connections with care.