The SE846 wins in terms of clarity and resolution and has got a much tighter bass than the SD2 (for a BA based IEM, the SD2s bass is pretty lose and not precise - you can definitely hear that when listening to moderately fast to fast songs).
Both have got emphasized bass. Whereas the SD2's bass is evenly (gently) emphasized and shines a little into the lower mids, the Shure's bass is more emphasized and rises towards the sub-bass where it reaches its climax.
Both IEMs have got about the same treble extension with a rolloff about above 10kHz.
The SD2 has got a wider soundstage that also has got more deptht. Overall 3-dimensional presentation is better on the SD2 with a feeling of being on sthe stage.
Instrument display precision is better on the Shure but it lacks of the SD2's big holographic stage.
The SD2 sounds more authentic and is a great IEM for Acoustic music, Singer-Songwriter stuff, Jazz and other music that is rather slow.
With fast music, the SD2 loses a lot of precision and its stage starts collapsing, not to mention that the low frequencies start to lose precision.