I tried both the T6 and S6 (round) cello bows. Under the ear, the T6 seemed to have richer overtones than the S6. However, when I recorded my playing from about 15 feet away, it was very difficult to tell the sound from the two bows apart. The big difference was the playing responsiveness. The S6 was easily more agile than the T6 and did, under the ear, sound more focused. It does take a few days of playing to get used to Arcus bows. After a week, I ended up choosing the S6.