Since time immemorial, iPhones have been sold in several different capacities and priced differently accordingly. But only you know how much space you really need.
It depends on several factors, which we'll go over together. The most important one is of course what you want to use your iPhone for, and if you want to record videos or take photos, it's best to get the largest capacity you can.
Because recording and taking good quality photos can take up a lot of space, and if you install some apps to edit photos etc., a smaller capacity may not be enough.64GB
This option is the cheapest, but almost no one recommends it. Still, there are many users who don't have that much money and still don't need that huge storage, so 64GB is perfectly fine for them.
I myself use 64GB and since I'm not a heavy user and don't download many apps or media it's absolutely enough for me. But if you have money for it, definitely get a larger capacity as you never know when you will start using your phone a lot.128GB
Here's the middle option that probably most people use. 128GB is really quite a lot, so you shouldn't run out of space on your iPhone.
It's a bit more expensive than the original 64GB version, but if you could use more space or you record some videos occasionally, we definitely recommend getting at least the 128GB version.256GB
With most iPhones, this is already the biggest option, so if you want the biggest spot definitely go for this option. There really should already be room for just about everything on your iPhone, but we're still seeing even more options on newer devices.512GB
As mentioned, 512GB can only be found in newer devices from iPhone 13 onwards. But if you really want plenty of space this is the one for you as many laptops have 512GB and so your iPhone should almost never lose space.1TB
The last option is 1TB which is what most of today's computers use in a basic build. This option is so far only available on the latest iPhones 13+ and so if you want a phone with 1TB then this is the phone for you.
With 1TB you can already record basically several huge videos and you shouldn't even feel that you've run out of space on your iPhone. It's the biggest option that exists so far, so it's not quite sure what all you could use the space on your phone for.