Bows can make a huge difference in the sound (seems like stating the obvious). The qualities each of us wants in our bow may be totally different, but if you take a violin and play it with a bunch of different bows, especially bows with different weights, the sound you get changes with each bow. (Different shoulder rests even change the sound, if you use one. Makes sense, it’s attached to the instrument so it must effect how it resonates, and even more so with the bow.)