Let’s say I have a mage character who wants to “expand” their combat tactics, would it be easier/more efficient to learn to move in armor or learn to use weapons?
If you’ll give a moment to express my bias, I’d say learning armor would be easier.
Okay, let me explain that. I have a little bit of training with a sword. Not enough to say, “oh, I’m an expert on fighting with swords,” but enough to understand that there’s a lot of things to learn, and a lot I don’t know. Training to be effective with a sword will take a lot of time.
So, as someone with no armor training, that much be much easier right?
Kinda, not really. Training for heavy armor requires a lot of conditioning. So, theoretically, it’s easier to learn, but when you get to the physical training, that could take longer, and would require a serious commitment.
So, when you say, “which is easier?” That’s going to depend on the individual.
“Which is more efficient?” Is going to be more relevant to the specifics of your world, and your character.
There’s a lot of potential factors for how magic works in your setting that may heavily influence your character’s choice. An example we’ve talked about in the past is D&D’s arcane spell failure rules. These meant that wizards (and most arcane casters) could not wear armor, without it impairing their ability to cast magic. In turn, there were ways where a wizard could train to use a sword or other melee weapon setup. So, effectively, armor was (usually) not a viable option at all.
Warhammer 40k’s setting offers the opposite option, where psykers (mages), in some cases, can ignore fatal wounds for days. Meaning, weapons are far more valuable than armor.
While 40k trends into absurd power creep, it can be worth considering that mages in your world might not be particularly worried about physical threats. It’s also worth remembering that 40k has a special class of melee weapons (force weapons) that can only be wielded by trained psykers.
Much like your world, the kinds of magic your character practices can have a huge effect on whether they want weapons or armor. An example from D&D is a low level wizard spell called Mage Armor. This will provide the castor with a fairly significant defensive boost (roughly equivalent to wearing some decent armor), and will last for hours. They also have a spell called Shield which can be added on top of Mage Armor, and offers some additional protection, though only for a few minutes per use. When you put these two together, you can end up with a few minutes of armor, without penalty, that rivals full plate.
If your mage has access to those kinds of defenses, then why would they need armor? There may be situations where they would need them. Both D&D and 40k operate with variations of magic canceling fields, and if your mage is dependent on conjured armor to protect themselves, or worse, prevent bleeding out, getting hit by one of those would be a very bad thing. By the same measure, if your mage is dependent on their spells for offense, and they end up in an anti-magic field, they’re not going to be able to do much.
In rereading Mage Armor’s description, I’m reminded of one of the quirks of that spell. The armor itself is, technically, an ethereal field, rather than a physically conjured (and visible) object. This means it actually protects the caster against ethereal foes who can pass straight through conventional armor. This sets up interesting, potential, interactions, and it is the kind of intricacy that can help “sell the reality” of your magic system.
If your character expects to deal with foes who can bypass magical defenses, then physical armor is going to be something they need. Similarly, if they’re dealing with foes who have magical immunity, then resorting to physical attacks may be necessary. Either directly, or by ensuring they have soldiers or mercenaries to do the stabbing.
Another consideration is what your character’s magic can interact with. I mentioned 40k’s force swords a minute ago, but if your character has the ability to temporarily enchant their weapons or armor, that might be a significant consideration in their choice of which to learn. Or, if your setting supports it, you could easily see a battlemage who specifically focuses on channeling magic through their gear. If your mage can empower their weapons and armor to superhuman levels, the correct answer of, “which should I choose,” may be both.
So, which is easier? I’m not sure. It could go either way, though as I said at the beginning, my biases lean towards believing armor is easier to learn.
Which is more efficient? That’s going to depend on what’s possible with magic in your world, and what powers your character has developed.
If you had to pick one, I’d lean on the sword. Not because it’s easier to train, or because it’s more efficient to learn, but because there’s more utility in it.
If your character is under threat, having access to a weapon (especially one that doesn’t reveal they’re a mage), is going to be more useful than having armor. You don’t want to go into combat without armor, but you really don’t want to go unarmed.
This also going to be useful if your character can conjure weapons. In that situation, their martial training will continue to serve them while they’re using magic, and if they do lose access to their magic (for whatever reason) they’re not immediately defenseless.
So, if you have to pick, take the sword. If you don’t, maybe both. It kind of depends on what your character is doing.