Solfege or not to solfege

In theory pedagogy class, we started to discuss the merits and downfalls of solfege systems. Here's a summary of the problem.

1. There are four systems of solfege in common use: a) fixed do (do = C); b) movable do, do-based minor (do = scale degree 1); c) movable do, la-based minor (do = scale degree 1 in major; la = scale degree 1 in minor); and d) numbers (scale degrees or semitones).

2. Solfege is fine for tonal music, but it begins to lose its utility as we approach the late 19th-century. It almost does more harm than good in post-tonal music.

What are the advantages and disadvantages of each system? Is solfege really neccessary? If you had to teach a sightsinging class, which (if any) system would you use? How might we facilitate sightsinging of post-tonal music?

Prepared singing vs. sight singing

Why study music theory, redux