i have an apollo and i have both the analog outs and the spdif connected to it. i have the spdif muted in console (which only mutes the monitor level). i have the spdif selected as the input source in logic. this means that i'm monitoring the analog inputs and can control the level i hear by adjusting the main output on the front of the axe fx (which is right next to me). the spdif signal is the one recorded (and is not affected by the main out control on the axe). it's just a workflow thing. i do boost the spdif signal a bit in console, using one of the uad plugins. i do notice a very slight difference in the quality of spdif vs analog, but it's very small. if your patches are basically mono, then selecting L or R should sound the same as selecting L+R in your daw. pretty easy to test by recording two tracks and then A/B'ing them. i'm not reamping, so the spdif signal is the same as the analog signal.