Hi Tom
To be honest, I need to spend more time listening to the Phone / Explorer2 combo to arrive at a duly diligent conclusion... but forced to make a choice right now, I'd probably say that the Mac SSD / Explorer combo sounds a little better than the Phone / Explorer combo.
I mention SSD above, as I believe the elimination of a rapidly spinning magnet within the case helps to reduce RFI / EMI within a PC... and that helps with producing better sound quality.
It's also possible that as a Phone has all sorts of Radio Receivers / Transmitters within a small space [Wifi, Bluetooth, 2g, 3g, LTE, GPS, NFC etc], that RFI / EMI within that space could be higher than in the more "spacious" environment of a laptop.
But ultimately, if you know and like how your PC to Explorer sounds, then IMHO the Phone to Explorer combo is 'at worst' a small step behind... and after more critical listening, this may not even be true... jury's still out.
However, I consider them to be two separate use cases... I travel a lot... so a lot of trains, planes, taxi's and waiting... so I wanted to see if the Explorer would add anything to my portable audio requirements... i.e. easier to use a Phone / Explorer on a train or taxi than a PC / Explorer.
I had already been using the above USB Audio Player to bypass the Phone's DAC and OS... so I wanted to see what the Explorer would add... and I have to say that it did add to my listening pleasure... enough to overcome the "hassle" of using a 2nd phone, with spare batteries and battery packs etc... and leaving my primary phone free to do it normal duties.
The main purpose of my post was to encourage those who might be interested in improving their Portable Music solution to at least try this for themselves... some here will have an Android phone... and some of those will have an Explorer... thus spending £3 on a USB OTG cable.... and another £5 on the USB Audio app... or a Tenner total, is not a lot to spend on an experiment to see if their portable music source can be improved... and that the hassle is worth it to them.
So, to answer your question... PC / Explorer sounds a little better... but the Phone to Explorer sounds great as a portable audio solution, including Apodizing etc., etc.
Cheers