There are a few aspects I'd raise: type of energy, looking at power vs. energy, and the most interesting one for me: lack of physical requirements / infrastructure.
Type of energy (and entropy)
Electricity is a low-entropy form of energy, so it's very organised, whereas heat is very chaotic. Converting from electricity to heat can be simple and efficient (just use coils of wire!), but the other way around is more complicated (we can get ~40% efficiency with some setups, and even then it takes a bit of engineering).
So: is the energy you're using high-entropy or low-entropy? Does it translate into some forms of energy more easily than others? (e.g. motion is easier than light?). What if you can only output one form of energy, and to produce light you need a "light generator" to convert it?
Power vs. energy
Something like a bullet obtains all its energy at once. However,
if your magical system allows action at a distance, then you shouldn't just compare instantaneous force/energy, but total over a period of time.
Say one magician can lift a cannonball (comparable to human muscle) - that means they can apply as much force as gravity can. If a second magician applies the same force sideways, the cannonball can "freefall" in any direction you like.
In fact - I'm capable of giving a heavy friend a piggyback. That means I can exert an extra force of ~1000 kilo-Newtons (on top of my normal standing around) for at least ten seconds. That means I can accelerate a 1kg weight to three times the speed of sound in only a second.
You asked "what would magic be able to do that we can't do better with electricity?". For that, I would respond with the biggest advantage that magic has in most representations: it requires no infrastructure.
So with a long enough lever I can lift pretty much anything - but I need space for the lever. With electricity, I can produce a bright light on demand - but I need to have placed a bulb and electricity source there first.
If magic can work at any kind of distance, then this requirement is freed up. I really can unlock the box with the crowbar that's inside it - more relevantly, I can easily walk through any door that can be opened from the inside. I can punch someone in their internal organs - or perform surgery without having to open them up. In the previous examples, I can accelerate an item without having to attach the energy source and conversion apparatus (like in a rocket) to the item itself.
This, I think, is often the most effective part of a magic system - even if you have to waste magical energy to get it in the form or place you want, you don't have to set up the physical infrastructure to deliver it, in the way you do when dealing with physical energy sources.
When viewed from a point of view of energy alone, it's easy for magicians to become insanely overpowered. If you want to avoid this, you could hobble the above properties - e.g.:
- an awkward form of energy that's hard to translate (and then a better generator/convertor could be a plot point / force for change)
- limiting physical distance to avoid extreme kinetic buildups
- requiring magical infrastructure (so spell-casting to launch something is the equivalent of building a catapult in "magical space")
- requiring physical infrastructure