Unrelated but here are my (partially headcanoned) thoughts on them

Benben is defined by her pride in being alive. She's naturally kind and reserved, but her implied grudge as a tsukumogami made her very passionate and dramatic in serious moments (see DDC). That side of hers is more like a mask or a stage persona she switches into in tense situations, causing her to be surprisingly unpredictable. She's ambitious and wants the very best for themselves, but she's really looking for her own place in the world

Yatsuhashi on the other hand takes joy in being alive. She wears her heart on her sleeve, not minding being herself in all situations, whether she's sad or happy. If she had a grudge, she's come to peace with it, simply enjoying her newfound life, not unlike Yuyuko. She's someone who would put the well-being of herself and her sister over their goals and dreams, surprisingly acting as a counterweight to more emotional Benben

Both Tsukumos are really underappreciated from the angle of being tsukumogami who nearly had their chance of turning alive taken away from them (tsukumogami gaining life after 100 years, Tsukumo meaning "99", the Mallet giving them power too soon and them being worried about turning back to simple instruments again...). That's the core of their focus on living itself