Well there you have it, looks like my work is done. I'm jealous of you guys man. You don't even need my impressions
The 901S and Plenue S are really very different. The 901S is crystal clear, with little to no inherent warmth. What it sacrifices in warmth, it gains in transparency and resolution. Notes are slightly leaner, but very forward and stimulating. The 901S embodies digital precision; 'digital' has a negative connotation, but it sets a high standard for technical ability that is hard to overcome once you're used to it.
The Plenue S is warmer and darker, with a more midecentric signature while the 901S is more tuned to the higher frequencies. Because of the smoother treble and darker background, resolution and transparency is not as great as the 901S. The Plenue S has a more coherent stage, being wider while the 901S is taller. In accordance with its signature and EQ, the Plenue S has thicker notes and more bass when EQ'ed.
Concerning resolution and transparency the 901S is better; in imaging and stage the Plenue S is better esp. balanced. Both have outstanding dynamics, but the Plenue S has better L/R separation.
The 901S has a world class performance that's hard to beat. But because of its wallcharger, UI and shape from the '80's, I only use it at home so it effectively gets 10%-20% of my listening time. I used to use the P1 on the go, and now the Plenue S. So if I'd have to choose one I wouldn't think 2 secs about it. But I do most of my listening out of the house.