It’s more like snow vs liquid water, if you’re looking for an apt analogy 
It’s really hard to answer that question without knowing what your horse is eating. I can tell you that I’m having amazing luck with my hard keeper on Purina Senior Active, Outlast and whole flax as his “hard feed” along with free choice pasture (or grass hay depending on time of year) and about 3 lbs alfalfa daily.
I couldn’t get my horses to eat Cool Calories. None of them would touch it. I recently added in Purina’s Amplify. So far I’m quite impressed. Its helping keep weight on while it heats up here and heads into summer. But I also have to say, my main horse who I originally purchased this for looks like he just stepped off of a movie set. The shine is absolutely stunning!
Another vote for Purina Amplify. It’s the only thing that’s worked for my OTTB. He came through the winter in great weight (and shiny!) for the first time in the 10 years I’ve owned him.
