My final words on all this, In my most humble opinion , It really isn't worth considering OTB unless you are investing in gear specialized for your stems and style of music. That's what I take home from this. early in this thread I established how NULLING an analog file a few times degrades the track to a point where you cannot tell the difference between ITB and OTB summing ( I'm not talking about additional hardware added). To my ears, digital summing changes analog with NULL processing. PLUS, By the time we smash the crap out of music, and it goes on MP3 ear-buds, who cares right. This is where most people are today. We are conditioning our hearing to appreciate high volume and the In-Your-Face sound. A sound that doesn't warrant investing in highe end converters and specialized analog gear.
But if we are trying to be better than that, speed up our ability to mix faster and enjoy music like it used to be valued, there is no doubt hybrid is my choice by a long shot.
More fun coming , I have an Orpheus here now and a DSD recorder coming this spring.