Zarkares: the benefit of this torso is that it has the highest HP of any viable torso (avenger has higher hp but the stats are so crappy on it its not viable for anything really unless its a pure phys anti phys which you never intend to deploy against other types). having a torso with good HP is very useful for energies as you wont have much module space or spare weight for HP plates. (most energies dedicate 1 or 2 at most to HP or resistence modules. this is due to your needing high energy stats if you wish to compete against other energies with it, if it is for use primarily against physicals or heat, you can probably dedicate more mod space to HP or heat stats however.
Windigo: the advantage this torso has over zarkares is firstly, its higher energy stats. this makes it more viable as a torso for making anti-energy energy mechs than a zark, where hp and heat stats are much much less important than energy durability where the goal becomes to drain your oponent and leave him a sitting duck before they do the same to you. Secondly, this torso has less weight, meaning you are able to equip more or higher level weapons and specials. Energy types are often weapon heavy builds with four or five weapons as well as often using a heavy drone, face shocker, and often use a tele, a hook or both. it will be easier to fit all this in with windigo as opposed to zark wich was the main factor which motivated me recently to switch to this torso.
Brutality: in terms of viability for use in energy mechs, this torsos time in the sun has came and went. don’t use it for energy. I had one of the most powerful energy mechs in the game using this torso for about the first month of reloaded, it was useful then as it had very decent cap stats aswell as a high HP (second highest of its time) while keeping w low weight. however, the zarkares has completely outclassed it in its two key bonuses - cap and HP. further to this, if you’re not after the high HP of zark, chances are you’re looking to target energy and so would be better off with windigo which has a higher energy regen stat than brutality. it could be said that this is a halfway point between the two, but in a time where 1v1 is gone and targetting is everything, this torso has become a sort of jack of all trades and master of none when it comes to energy mech design. while this torso will always have sentimental value to me, its with a heavy heart I have to recommend against you using it.
Grim Reaper: this was popularised as an energy torso in no small part due to toxic’s use of it. it has the highest base energy stats so is good for targetting other energies, but I’ve always found that the sacrafices it makes to its heat and HP stats, which are pitfiully bad, make it very difficult to use against physicals and heat. I hold it on the same level as Avenger as a not viable torso, personally.
those are my thoughts on some of the most popular energy torsos (plus britality since you asked about it in particular).