don't know if the 3 part is better, but I hear that we can tailor our nuts to better suit or plants needs with the various parts. The 3 part is a Micro nutrient, a Grow nutrient, and a Bloom nutrient. What this means is that you could push the envelope to the extreme by maximizing the amount of each nute for each stage of growth, or you could hold back on certain parts of the nuts to trouble-shoot of control growth.
I am a novice but I can see how having more parts can be a benefit to a guy like me who wants to grow, "outside the box" of normalcy and push/tweak the limits.