Hi, I ve seen both closely. In my opinion, Sweetheart is almost like fuschia (Sweetheart is a bit darker I think but still pink). Cabaret is like coral pink. Both are very beautiful, but I loveee Sweetheart. Maybe you too if you are looking for hot pink. Been eyeing on Small Hayden in Sweetheart, lol.
I have the Cedar Street Maise in Sweetheart Pink and I love it! It's a deep hot pink. It looks brighter in some lighting, darker in others. It's dark enough that in my mind it's a neutral I think it matches everything personally (or maybe I don't care.)