Bitcoin is better. I won't delve into altcoins, as you would need to carefully examine each of them, but most of them have major flaws. "Volatility" means freedom, it is the price people are willing to pay for something in the market, and the current representation of the global sentiment of buy vs sale.

Those that want it vs those that don't want it for whatever reason. No committee, government, politician, banker, foundation, conglomerate, company, etc; complete freedom. That is what a price freely fluctuating in the market means.

The rules of Bitcoin are established in its code, open for everyone to see. Those that agree with those rules, mine it and rune nodes, and they cannot be easily changes without the approval of the vast majority of those running them, true democracy.

Your government, or the foundation that "controls" your altcoin, can decide to alter the rules overnight. You don't want this, but cannot stop it. You think they would never do it as it hurts themselves, but you would be surprised what a few people with power can do. Any FIAT can enter hyperinflation, and it is but one executive order away from doing so. Imagine any excuse: A coup, a failed crop, military invasion, for those darn politicians to pull the trigger.

People want Bitcoin because its useful to them. They studied it and know its characteristics, and so did with the others and fiat. Those who are not convinced them sell them and those who are buy them, except traders who constantly buy and sell for profit without any special attachment.

But in the end the market represents the entire world sentiment. Sure some people may have more than others, and skew things a little, but in the grand show the free market is a peaceful and democratic resolution of conflict. Your vote is your wallet isn't just a saying, its a fact. When you buy you show support, and when you sell you show disapproval; no middlemen.

There is nothing fixed about fiat, if anything, it has guaranteed inflation, in varying degrees. It has both infinite production and infinite manipulation by very few people in control, its garbage.

Cryptocurrency is much better. It helps its user to make transactions more quicker, easier and efficient. You can make any transactions anywhere using lower fees. Another reason what I like the most is, it is not bring controlled by the government which avoids any conflict with economic and political issues. And also, the more people that uses crypto, the more its value will increase.

Before anything else, the definitions you've provided are somehow limited. First, cryptocurrency does not necessarily mean it has a volatile value. There are several stable cryptocurrencies, commonly called stablecoins. Libra, the controversial crypto project by Facebook in partnership with the huge names in the business sector, is also planned to be a stable crypto. Second, fiat currency is not just the hard physical currencies of old anymore. Fiat has already transformed into cashless with the use of cards and other online payments.

Anyway, in my actual circumstances, I cannot just easily choose between the two. A few online transactions are the only way for me to use crypto as a currency. Outside of it, it still has to be purely fiat whether in cold cash or card. We are still far from transforming into a digital society. Cash is still needed in my day to day transactions.

Well cryptocurrency is more convenient to use in transactions and investment business because with significant benefits it can happen but in the security of these funds there is no one waiting for an answer so most use Fiat to conduct daily transactions and their needs in their area if using cryptocurrency then it will not be able to because one region still does not use crypto in a day in his area.

So crypto is used for long-term and unlimited investment.

Yeah! Cashless economy acts as a big blanket which covers all citizens of the country and one can easily trace the source and destination of every transaction. Sweden is perfect example of this. But not every person prefers such system. When living in an independent democratic country, people want liberty and privacy in using money. They have argument that such system will only target citizens while leaders and politicians can easily do corruption. So even citizens should have anonymity and autonomy in doing transactions. Bitcoin was born as a product of this thinking. Now things have gone way ahead and projects like 'Digital Gold' providing anonymity in holding assets like gold which was almost impossible to even think of 10 years ago.

I like the idea of cryptocurrency, and I like having some of it. If there were truly an option to pay for stuff with Bitcoin and not overpay with the fees or anything, I would prefer Bitcoin over fiat. For now, however, Bitcoin is way behind fiat in terms of adoption, it has scalability and recognition issues. For example, I am going to need to apply for a visa in a few months, and I'll need to prove that I have some money to live abroad. For that, I need a bank statement. I have enough money in Bitcoin, but for it to count I have to sell it for fiat, I cannot provide a signed message to the Embassy. Such things are serious obstacles for me.

I think right now there is no comparison b/w the two. Fiat is well established and we use to live our daily life on fiat.
Crypto is fairly a new concept and it will take quite a while before we can give a verdict that whether its a match to fiat or not. The only way it's used is to store value not as a payment system.

With all regulations crypto is getting closer to fiat, its impossible to spend crypto without strict KYC on most popular services

The never-ending debate on who's superior and who is not. I guess there will never be an end for such a comparison between the two since one can always be better than the other in different aspects. For instance, fiat can be accepted anywhere in the world whereas bitcoin is only accepted by a select few. Bitcoin can be sent across borders without having to painstakingly fill out some forms while fiat cannot. You see, depending on the situation, any one of those currency can be better than the other so it's pointless debating this over and over again.