All spells and abilities are not equal. Even when they are equal.

JOLT (3 mana): 1 damage to an enemy within a range of 3 spaces.
Jolt is a very simple, cheap damage spell that has an above average range. It always costs 3 mana, it always does 1 damage, and it always has a range of 3 spaces. Right now, 3 units can cast Jolt. Yumboe Battlemage (Parada) and Eloko Grand Druid (Parada) and Island Umlingo (Zermano).
Let’s look at these 3 units, and more specifically their Jolt spell. (Let’s also take this from the perspective that we have 10 mana to use on spells- same amount that you begin the game with.)

Island Umlingo is a cheap unit in the Zermano warband. At 3 gold, it’s a pretty good value for a unit that can deal a bit of damage over a range of 3. It’s got an above average Rank as well, so it’s got some good things going for it. When looking at the Zermano lineup, however, it becomes quickly apparent that there are simply a lot more spells that are a lot more impactful that certainly take mana priority from the Umlingo. Lighting Bolt, Vaporize, Ice Missle, and Blizzard all are much better, while Fire Orb and Skypierce can be more useful depending on the situation. There is only 10 mana to go around, and much less after one of the more powerful spells is used.
If Jolt becomes a lower priority, then so too does Island Umlingo, because it is not going to do much else. However, if there is either a drastic need or an abundance of mana, Island Umlingo still serves a valued purpose. Since it generates mana, it can serve as a resource gatherer as mana is crucial to Zermano’s success. If there is an extra 3 mana available and a low health enemy unit, Island Umlingo can zap it, and if Zermano is strapped for gold but needs to take out a severely wounded threat, the Island Umlingo could get the task done cheaply.
Now let’s look at Yumboe Battlemage’s Jolt:

At a glance, it’s easy to see that this is a far more versatile unit than Island Umlingo. The Yumboe Battlemage only costs 1 more gold, but has a higher rank, is a Captain, can fly, and has better movement. Additionally, it can dodge ranged attacks and spells with Evade and attack diagonally regardless of terrain tile with Agility. Oh yeah, it has Jolt too. With all of those other skills, Jolt must be an afterthought right?
Not so fast. YBM’s speedy movement of 3 means that it can organically double the reach of the spell simply by moving first. Its 4 rank also means that it’s likely going to be one of the first units to activate. Add that 3 speed to the range of 3 provided by Jolt, combined with a high rank and suddenly you have a spell that has the capability to hit any unit in any part of the map probably before your opponent can get out of the way. That is an incredibly useful spell to have. Having flying is a big deal as well. YBM can either land or be Aerial when casting Jolt, meaning if there is a unit on the battleground that is not immune to spells, its an eligible target no matter where it is at. How about Evade 5? That plays a factor too. The Battlemage can be aggressive with it’s speed, and therefore aggressive with it’s Jolt because Evade 5 provides it the confidence that it can dodge return fire from spells or ranged attacks.
Most importantly, Yumboe Battlemage’s Jolt has to contend with Parada’s other spells… which are Tornado (awesome, but situational) and… another Jolt. Basically, YBM’s Jolt is the most useful spell Parada has to offer, meaning YBM will almost always have the mana and opportunity to cast it.
Despite Jolt being the same spell, it is far more useful, dangerous, and available for the Yumboe Battlemage than it is for the Island Umlingo.
Finally, let’s look at the Eloko Grand Druid’s Jolt:

Same Rank as the Yumboe, slower speed, and no flying. The Eloko Grand Druid can be extremely poweful- if it’s casting Tornado. If the situation does not call for Tornado, then EGD’s Jolt becomes not only much less useful than the Yumboe’s but also than the Umlingo’s.
Here is why: The sheer power of Tornado drives the Druid’s gold price up to 7. That’s a more than double what the Umlingo costs. Unlike the Yumboe Battlemage’s abilities, Eloko Grand Druid’s other spell (Tornado) does not enhance Jolt at all. In fact it overrides it, because spells require the activation to use. Also, generating mana does not help the rest of the Parada warband, and there are plenty of mana-free ranged options for Parada. The Eloko Grand Druid suddenly becomes almost the same unit as the Island Umlingo, just at more than double the price.
Spells and abilities in Factions: Battlegrounds rely a lot on the unit that can cast or use them. Sometimes they are much more effective with one unit or faction than they are with another… There are plenty of examples… Share some that you find in the replies!