Comparing the two instruments in terms of timbre diversity and timbre expressiveness, the saxophone has a better timbre.

1. Diversity of timbre: The timbre of the saxophone is more varied, and various timbre effects can be achieved by adjusting the mouth shape, breath and reed. In comparison, the trombone's timbre changes relatively little.

2. Expressiveness of timbre: The timbre of the saxophone is more expressive in expressing emotions. Its timbre can express a variety of emotions such as tenderness, soothing, and passion, and is suitable for playing various styles of music. The trombone is relatively weak in terms of timbre expression, and mainly has a low, rich tone.