Butter Treat and Heavy Cream are my two favorite deep conditioners. Here are the differences:
Butter Treat is meant for people who have extremely dry, unruly or rebellious hair. It can also be left in the hair for more intense conditioning.
Heavy Cream...they just reformulated this. They added Gold Camelina (which adds shine) as well as Olive Oil (which provides inside-out conditioning)+ the other key ingredients such as avocado oil(Provides silky softness) and silk amino acids (adds strength). Heavy cream is meant to control frizz on extremely dry/brittle hair.
So basically, the difference all comes down to depending on your hair type. I personally switch back and forth on these two myself. I love the All Soft line because I have medium fine hair and I get frizz and I also can get very dry. But if I had coarse hair, I would probably use Butter Treat.
Does that help at all? What is your hair type?