Comparing systems through phone recordings

It can never be done, no matter how much refinement you put into the process.  The particular room one records in is unique in its characteristics, so how can any meaningful judgment be made?  There is no perfect microphone--in studios, many different types and models of microphones are used just because they each have certain characteristics and the selection is made based on the particular instrument or vocalist, the particular effect that is being sought, etc.  How can ANY microphone be selected, even if one had a range of alternatives, that does not then make the resulting sound "objective" in terms of a realistic reproduction of the sound in that already arbitrary room?  And what about microphone placement, recording technique/engineering?  

Then there is the matter of the playback of this recording.  How in the world does one account for the gear, the speakers, the acoustics on the playback end?  

Is there any harm in at least trying?  Yes, in that one can easily be deluded into thinking that the reproduction is good enough to make an evaluation.  It never will be good enough to have any meaning.

Why even consider expensive, high quality gear if a phone can deliver at least as much?  Do you really believe a phone can record and deliver a signal that allows one to discern subtle differences that are the product of very expensive engineering and build?  Why would a recording studio bother with $20,000 microphones if the ones in a phone can deliver enough quality that one can hear what that microphone brings to the recording?  

I expect there to be obvious differences that one can hear even with a phone recording, but, there is no way to tell if those differences are the product of what particular gear are doing and not just differences in the recording process.  In other words, the comparison would be worse than useless because it would most likely lead to false impressions.