I have UK and US dual citizenship (I was born in the UK and married an American, naturalized about a year ago).

Advantages:

• Easier entry into both countries, and countries with appropriate treaties with one or the other. This is somewhat important to me under the current US administration.
• Will allow my wife to get UK citizenship more easily should she want to.
• I can vote in elections in both countries. Also important with the current US administration.

Disadvantages:

• US citizens have to file/pay taxes no matter where in the world they live. I believe the US is the only country that does that - although this does apply to all American citizens, regardless of dual citizenship; I only mention it because dual citizens can more easily move out of the US.
• I need to keep track of two passports, especially when traveling, although I only need to show one at a time.

My son and daughter are citizens of the country they were born in, but could choose to acquire citizenship of their mother's country of birth, by descent.

For my daughter, this might be a nice-to-have as it would make things easier for her if she chose to reside there for any period of time.

For my son, it's a more complex choice as he would be required to complete military service in that country. For some teenage boys that might be the adventure of a life time, for others it would be a nightmare. I'm planning to let him decide what he wants to do.

There is no dispute in rescues. Whoever is there first can take them. That's just practicality. You're not going to leave your own citizen there when you're there for a rescue. Outside of that context, you're subject to the laws of the nation you're standing in.

Emotionally it's definitely a good thing, anyone who hates their country of birth can renounce their citizenship but I have simply built a good life elsewhere and wouldn't want my old passport involuntarily taken away from me, it's emotionally valuable to be able to go back and show the old passport and be welcomed just like one has always been, even if my daily life nowadays is somewhere else.

Depends on which country you want to choose for the second citizenship.

A British person with a German passport is also a German citizen. So they can't not help them if they have the means.

I don't know about the Brits. The Germans have some tight rules about dual citizenship. It will be an exceedingly low number of people who qualify legally on both sides for dual citizenship of these two countries.

As the revolutionary guard troops surround Dubai, this probably would not matter. They would try to get people out and I'm sure both Brits and Germans would evacuate each other's citizens if it meant death if they didn't. But if the situation allowed for more thorough investigation, I probably wouldn't mention my other citizenship to the Germans at least.

Many folks of Turkish descent but born in Germany used to take up German citizenship and had to renounce the Turkish one in the process. But they were able to get it back once the German passport was done, which could be grounds for revocation by the Germans if they knew about it. In Japan it's even harder to have two passports; kids of mixed couples often have two passports but they're not supposed to from the Japanese side. So they wouldn't make this known to the Japanese embassy who would care about this if the revolutionary guards were still far enough away to have a closer look.

I would not be surprised if there was a bit of horse trading going on between the embassies. So if a dual citizenship holder was rescued unconscious in a drone attack, it's probably the first delegation on the scene who takes charge of the case. Until the victim regains consciousness and possibly decides something else - if they can without causing more trouble for themselves.

I have no experience with this so my guess is really just that. If two consular outfits arrive on the scene to help our unconscious victim at the same time, they would probably try to figure out: what's the country of residence for the victim? If it's not a third country, residencistan trumps the other one. If it is a third country, then where are the next of kin. If there are none, probably country of birth. If that doesn't help they do a game of paper, rock, scissors.