iPhone 12 vs 13

Why would they need the latest software? Virus protection? I know plenty of old phone owners who have never had any problems, it's about how and where you share your personal details. Prevention. Common sense is a stronger enemy of viruses than the latest software.

Connectivity to other apple devices and the IOS system can both happen with an older model iPhone, buying an older one will also reduce waste.

You can get a much better camera and a perfectly functioning phone for half the price of an iPhone 13

People who need processing power for things get a laptop or a PC, not a tiny phone. If they can afford an iPhone 13 and need processing power, they'd be better off buying a cheap phone and a gaming PC.

Newer software also has more features and a new phone will last longer which reduces waste.
How old are we talking here? An iphone 5s doesn't support apple pay, iphone 11's don't have 5G connectivity.
That's not the point- a camera can be bulky for some people.
Can you play mobile games on a gaming pc?

viruses work by exploiting vulnerabilites in code. it's not really much to do with sharing personal data
additionally outdated software gradually becomes behind in featureset and app support

depends entirely on the phone and the features you want

and then you have to carry said camera and phone everywhere

mobile gaming, editing on the go, some camera features etc.

You are creating waste by buying new things while there are old things that work and are thrown away. It's just adding more stuff to a system with too much stuff.
I phone 5 may not have apple pay but what's wrong with using a bank card? Ok so iPhone 11 doesn't connect to 5G... and? It's not like 5G allows you to do things that 4G doesn't. If they need a camera for professional work, they should use a proper camera because it is much better quality and has more settings. If it's just for personal use, there are very good cameras on older or cheaper phones which work just fine.
Can you play mobile games on anything other than an iPhone 12/13?

I bet the op is like 'wtf is going on here'

HAHA, YEAH! I just wanted to know which one to buy and it's erupted into argument!

Brand new iphone 12's aren't already in the system. It doesn't make a difference so a phone that will last longer will be better for reducing waste.
Contactless has forces you to type your pin in after a few uses. Using biometric authentication like face id or touch id is much more secure than a pin. Plus it's a backup option incase you forget your wallet. 5G literally has faster speeds and lower latency than 4g, it's not the same.
ofc professionals have their own camera. Most people don't need a seperate camera for normal use.
Some people might care about the 120hz refresh rate that the 13 pro offers. Also faster processing power means less lag and higher fps.
anyways the whole point of this is that people want to have luxuries to improve their day to day life, it might not mean that it's necessary but it's their choice.

If an individual has no other option but to buy a new phone then the sustainable choice would be to get the best quality one you can find. But that is not the case at all! There are tens of thousands of older, perfectly functional phones which have been discarded by people who want to be 'up to date' so if you really cared about sustainability, you would first use up every second hand phone available until they are completely unusable before buying a new phone.
While I've never had to use a pin for my card after activating it, I could agree that apple pay may be safer. But so what? Apple pay also works on the hundreds of refurbished iPhone 6's available for under £100 no need for an iPhone 13.
And the only camera good enough for casual photos Is the iPhone 12/13?
Again, why do you need 5G speeds when 4G works? If that is the only reason for upgrading to the latest phone, just don't do it.
Who needs a 120hz refresh rate? Really? Why don't we just buy diamond encrusted door knobs or use African blackwood in our rafters
Since the OP is on a forum for students, I hope I'm not making too big of a leap when making the assumption they are a student. I can speak with certainty when I say having the latest phone will not make them a happier person or improve their day to day life. Infact, I can point to many studies which conclude that phones have a net negative effect on (particularly young people's) wellbeing.
It's not necessary and it is their choice but I know it's the wrong choice from a personal, environmental and economic perspective.
I hope you realise that such luxuries are not necessary for happiness or improving people's quality of life student or not.

Even from a sustainability pov, buying a brand new phone and using it for 6 years (which is what I do) makes no difference to buying a 3 year old phone and using it for 3 years x2.
Back to the point about softwares, iphone 6's are already obsolete as they cannot upgrade to ios 15 so it's not likely to last. Most would be on their last leg and suffer from overheating, battery degradation among other issues.
People also have preferences when it comes to camera quality.
Why have lightbulbs when candles work? If that is the only reason for installing electricity, just don't do it.
Technology evolves with time, more applications for 5g will come out and it's part of future proofing your phone to make it last longer since OP is already upgrading. If people didn't adopt electricity back then, new uses for it might not have been invented, same can be said for 5g where we need widespread adoption for developers to find new uses for it.
I pointed out 120hz because high refresh rates are important in gaming
If OP is deciding between an iphone 12 or 13 it means that they have the financial means to buy them. The studies show having phones make people miserable, not the latest phone. If you want to prove anything with those studies then your conlusion should be that people shouldn't have phones and go back to the 80's.
anyways some features in a better phone can make someone's life easier even if it doens't affect you directly.