The angle-to-brightness curve can be adjusted as needed to avoid under or over-emphasizing mountain slopes. The "Andes" example is probably a case of exaggerating topology to illustrate relative differences, and NOT in inherent fault of slope-to-brightness maps (DBM-like). I can't say which one is more practical without going to the actual slopes to check the look and feel of the terrain and "feel" of the slopes. For technical accuracy, color coding is probably better (color-per-height), but slope-shaded maps are easier for regular folks to relate to.
Ray tracing is probably better when dealing with direct shadows and reflections, such as found with buildings. But for high level maps with mountains and rivers, I believe DBM is just fine if tuned right, and won't differ noticeably from comparable ray tracing.
To avoid misinterpretations, the large-scale shading should more or less mirror a semi-cloudy day such that direct shadows and reflections would play an extremely minor role anyhow.
I should point out there is an element of subjectivity here. Illustrations often exaggerate to emphasize various attributes of the illustration's target. Often there is a trade-off in terms of aiding the quick mental digestion of information versus "native" accuracy. Abstractions lie on purpose, or we wouldn't call them "abstractions".