I feel like a more appropriate - or at least a more interesting - comparison would be “fix the old one” vs “replace with new.” Replacing an old broken product with a new unbroken one is changing two variables, not one.

Now, if the author would like to break their New refrigerator and report back, I’ll take it as an interesting result.

Can you even fix the 30 year old one... that's still '95 when these things weren't very fixable.

But at the end of the day the question is what is the likelihood the old fridge will be in a semi-broken state.

Usually the older ones are easier to fix. It's never going to be new of course, and even stuff like the insulation will be degrading with time.

I'd argue that in general, refrigerators are one of the few devices that came out of the energy efficiency mandates as better products.