I'm not Rob (or anything close to it
) but my take is that the Hugo will play both formats, so why ask the player (iPhone Onkyo player) to do conversion to PCM when you don't have to. Leave DoP enabled and that way what is DSD stays DSD (actual recording provenance notwithstanding of course) into the Hugo. The bigger issue is to be on the lookout for the best version of your recordings. For example, if you like BIS's music, don't buy their SACDs and rip them to DSF (or DFF) but instead buy them at their native resolution on the eclassical site. This native resolution may, in fact, be as low as 24/44.1k (for their early recordings that appeared on SACD) but it's the closest to the master, if not the master. On Chord DACs (cuz they do PCM so well) it's a big enough improvement to care to go out and find this stuff.
My "tip" is mostly for stereo playback. Since BIS (same example) doesn't sell their native PCM surround tracks you'll need the upsampled DSD 5.1 on the SACD for that..currently.
Net/net, if it was recorded/mastered in PCM, buy it and play it in PCM. If it was recorded/mastered in DSD (or analog-to-DSD) then play it in DSD. Sometimes one format is all we got for hirez, so even if the original material was PCM, if the higher rez PCM is not available to buy you may find that the kidd glove treatment to get it remastered on SACD may be enough to pick that format (over, say, the 80's redbook version). It's a lot of work, sometimes, but in the end we get as close to the master tape as possible. This work makes those faux upsamples that appear constantly on the hirez market even more frustrating to see.