If missiles can be compared to real life ballistic weapons, it could be compared to a hand-held anti-tank grenade launcher, or as many commonly know it by: a rocket-propelled grenade launcher. Samus’ missiles may also utilize what’s know as the Munroe effect,  the reinforcement of shock waves in the concave, hollow end of a shaped charge, producing a greater resultant wave and concentrating the explosion along the axis of the charge. In other words, these missiles could be described as high-explosive anti-tank (HEAT) warheads. Why? In Metroid: Other M, upon encountering Adam, Anthony, and the others, Lyle lets Adam know that the explosives are ready, but upon his attempt at destroying the barrier wall, it remains intact. 
Anthony explains they “tried using explosives, but it’s tricky to pull off without collateral damage.” What they “need is some way to focus the power onto one centralized location . . .” This is where the Munroe effect would come in. All the energy wouldn’t be spread out, but would be focused, delivering more damage. We see this a few times in Metroid: Other M, such as when Samus shoots at an ice wall, ice cylinder, and metal sphere.  This still doesn’t tell us how powerful Samus’ missiles are, however. While I could settle for the amount of explosive material is present in certain warheads, I still wouldn’t know how to determine which one to use. I suspect an alternative would require the use of G. I. Taylor’s dimensional analysis. 
We know that RPG warheads use HMX or RDX. I’ll settle for RDX because it has a lower detonation velocity of 8,750 m/s, while HMX has a detonation velocity of 9,400 m/s.  To find out the diameter of the blast from a missile, I will use Nightmare’s face, which is covered by the explosion of a single missile. In fact, the explosion slightly passes the face. I will have to use Nightmare from Metroid Fusion because it’ll be easier this way. Samus stands at 104 pixels. Due to her hunch in this game, I’ll assume she’s standing at 1.8 m., not 1.9, her original height. Nightmare’s face is roughly 158 px., which is 152% the length of Samus’ height. This turns out to be 2.73 m.
While it’s difficult to find out the distance traveled at the detonation, it seems there are four parts to the explosion, which means I’ll use a quarter of this diameter and divide it by 8,750 m/s. Using G. I. Taylor’s dimensional analysis, I end up with roughly 30 MJ of energy, which is equal to 7.16 kg. of TNT.