Shubert,
Thiel's don't really favor any genre of music, but as Thiel's are less colored and closer to laboratory grade instruments than most other speakers, they will reveal the truths (more on this later) before them. Thiel's aren't necessarily better than other speakers in any specific audiophile ways, but completive with all of those audiophile speakers in all the various characteristics (with proper equipment and set up) without the downsides of those speakers that are one and two trick ponies. They are extremely balanced in everything they do. The only limiting factors are room and what precedes them. IME, classical music tends to be better recorded than most popular music. With proper room size and dimensions, and ancillary equipment (especially amplification) the larger Thiels they can excel at symphonic music. If the recordings had microphones placed deep within pianos or immediately above the violins, the lack of time for the sound to bloom can lead to perceived hardness. Sometimes to truth isn't so pretty. But I for one prefer that over the syrupy, rose colored glasses perception that other speakers seem to gloss over everything that comes through them, whether they need the it or not.
All Thiels need to be at least 8' from speaker directly to listener for proper driver integration, and the time coherence that is such an integral part of the Thiel designs.