High, medium, or low

If a volume of songs comes in a choice of high or low keys, I will go for the high ones. If the options are high, medium or low, I usually choose medium, not seeing much point in using gratuitously high keys when I can reach the lower extremities easily too.
At the moment, I’m learning some Schumann songs from the ‘high’ Peters edition. My teacher suggested ‘Stille Tränen’, until we went through it and found that it was in C major. While this is within my range, it is not comfortable with two awkwardly placed top A’s and an (optional) B flat! To say nothing of the breathing problems I would lay up for myself by doing it in this key. Meanwhile, the lowest note is the G above middle C. Elsewhere in the volume ‘Die Nonne’, for example, has a range of middle C to the second E above it. So why isn’t ‘Stille Tränen’ in (say) B flat? I can think of a couple of possibilities:

a) perhaps Schumann originally wrote the song in C and the editors wished to preserve this
b) the song wanders into a remote key in the middle section. If it were in B flat, both singer and pianist would be confronted by double flats. But the difficulty of reading these would go once you’d learnt the song, while those high notes remain as high as ever!

The most demanding range I’ve seen in an edition offering a choice of pitches was a song in a ‘low voice’ edition of Samuel Barber which went up to top C! I assume that this particular song is only done in one key.