I'm looking to get a new 17'' laptop and I have been interested in i9's for awhile, but I don't know if they are worth the extra money.
Unfortunately, this is the problem with most people in the world today, that they have much more money than sense and they need to be able to show others how rich they are. At the same time, people with intelligence, education and skills do not have very good incomes in this world, and they have to buy cheaper, but at the same time not worse, things. I recommend you to buy what you need, but not what is just or only more expensive. More expensive is very often not better in any way. Expensive things are simply necessary for the rich people to be able to appear better (read dumber) than others.
of course a I9 is more powerful than a I7 if you can afford it run it...i would...but a I7 seven Gen and up with 16GB of ram and a NVMe drive should give you all the performance you need....now if your a hard core gamer thats a different story you need between 2K to 3K depending on what you want to build or buy.