Soylent has better quality taste, balanced nutrition.
The Soylent (2.3 lbs 4800 kcal v 1.8 purchased about 2 months ago) taste much better quality than the Slimfast powder.  Also I like that the nutrition in Soylent powder is balanced - if you drink 400 kcal worth of Slimfast powder at once you'd get too much of the vitamines and sugars and get a metallic after taste.
Rating: 4 stars