As I take on the former, which is in the form of an Argentinian Tango, the sounds which I draw from my instrument are naturally raw compared to some mainstream classical works. I find myself visualising myself dancing, and upon reaching the offbeat accents, I would whisk my partner in an exciting and quick turn around the dance floor. It's probably due to my subconscious acknowledgment of the more exciting and surprising nature of those accents that gives rise to the raw touch.
In the latter, I was working on the first movement. Even if the music comes to an intense climax, I find the sounds which I attempt to caress from my instrument are well rounded and refined, seemingly trying to present those emotional moments in a more palatable and most poetic manner. In the sections leading up to those intense moments of the music, my fingers produced their most delicate touch and attempt an elegant dance above the strings. Dramatic still of course (as what Schubert would like to express), but in a special blend with musical poetry in the passages (as his usual distinctive style).
It certainly seems that the knowledge of the composers' lives, their compositional style and the societies in which they were living in does contribute to these subtle yet important variations in touch when playing their music. Passages with an almost similar texture and even harmonic progressions have different significances in different works and thus, are treated differently.
P.S: I would like to express my gratitude to a fellow musician based in Brazil, Xan, for helping me out with the pronunciation of Piazzolla's Verano Porteño and for all the information of the Latin American music which he has given me. That certainly helped in my interpretation and understanding of the music.