What are the advantages of using the Intimidate skill over using the Diplomacy skill for the same purpose?
There are some pretty obvious downsides to intimidation. The primary one is if it fails you may end up with a bunch of city guards on your tail. What about the advantages? Because from what I, in my limited knowledge, understand, intimidation is just the worse option, due to the potential repercussions being notably higher. Odds are I'm very wrong about that, which is why I asked.
In some situations, Intimidate can be successful on a much lower roll than Diplomacy. RAW, the DC for an Intimidate check is 10 + the target’s Hit Dice + the target’s Wisdom modifier, and success automatically makes the target Friendly toward you for a short amount of time.
By contrast, Diplomacy with an Unfriendly creature has a DC of 20 + creature’s Cha Modifier, and a success only improves their attitude to Indifferent; you'd need to succeed by 5 more to improve it to Friendly. Diplomacy with a Hostile creature often isn't possible, but it has a DC of 25 + creature’s Cha Modifier, and usually only improve their attitude to Indifferent at best:
Diplomacy
Succeed – If you succeed, the character’s attitude toward you is improved by one step. For every 5 by which your check result exceeds the DC, the character’s attitude toward you increases by one additional step. A creature’s attitude cannot be shifted more than two steps up in this way, although the GM can override this rule in some situations.
Of course, this can work in the other direction as well. Because the target's Hit Dice affect Intimidate DCs but not Diplomacy DCs, Diplomacy may have the lower DC when interacting with high-level targets (again, RAW - it's not uncommon for published adventures and DMs to alter these rules).
The primary advantage of Intimidation over Diplomacy for those that use it is that you use your Intimidation ranks on the check instead of your Diplomacy ranks. Since Intimidation is also useful in combat for demoralizing foes, warriors often take ranks in Intimidation—and then since they have those ranks, they might want to use them in other situations as well. Warriors are often rather tight on skill points, too, so taking ranks in both may not be a realistic option.
Obviously this will vary from GM to GM, but as Diplomacy is supposed to represent negotiation using suitable etiquette and manners, a GM could decide that even a successful check involves some manner of compromise. You get what you want per RAW, but maybe in exchange for that you have to give something up. A good GM will tell you this before you make the check. When my players want to do a Diplomacy check I ask them how they plan to convince the NPC. That plan may be purely verbal persuasion, but it could also involve promising to do something for the NPC or offering them a gift.
On the other hand, with a successful Intimidate check the only thing you give up is the attitude of the NPC. To be fair, there can be consequences to this, like getting reported to the authorities, as the rules say, but perhaps the reward of not having to give anything up to the NPC outweighs the risk.
It depends on how much time you have to spend. Diplomacy typically represents a reasonable amount of back and forth negotiation that could span several minutes whilst Intimidation can be as quick as a single threat and a show of steel.
When using Diplomacy, you also typically take their opinion into account for the DC. They may be friends, enemies, random bystanders, sycophants or someone you accidentally insulted. After all, it's much easier to convince your old drinking buddy to let you into a restricted area than it would be to convince the xenophobe who thinks adventurers are little better than hobos.
Conversely, Intimidation doesn't care how much the person likes you, it depends on whether they believe you can make good on your threat. Of course, if you regularly intimidate your friends, they may not be your friends for much longer.
This we come to our final difference. Consequences. Intimidation is typically quicker and easier for your average burly Warrior to get what he wants, but it can leave a mess. Diplomacy takes longer and make cost concessions, but is less likely to bite you in the long run.
Depending on the situation, some NPCs might respond better to one approach over another. Those that respect strength over words might be more likely to respond to a forceful approach, such as using Intimidation. This could make the DC lower, or give better results from a successful check.
In other games I GM'ed (not specificially D&D), I explained it to players as the following...
EG:
Intimidating Ira intimidates the guard to let her in.. NOW. She succeeds. But, no one likes being bullied. So, the guard may go call for help once she's not around. Or, they may remember her later on in a random encounter on the streets where they have more guards around, so they immediately start a fight with her.
Diplomatic Dave lays on the charm and talks the guard into letting him in. But, the guard says now isn't a good time, because Dave might get caught, then the guard gets into trouble, etc. But, if Dave comes back in about 15 minutes, the guard will conveniently be off taking a 5 min break with the door unlocked allowing Dave to slip in.
Both got what they wanted, but Intimidating Ira got it now while Dave had to wait. But, Ira also ruffled feathers while Dave did not.
