My guess is there's nobody here that's able to do the comparison. There are just too many variables. Not to mention that unless a headphone comes in both USB-C and 3.5mm, it would be impossible to know how it compares to itself.
I'd wager that 3.5mm headphones are a better buy, though. Because the USB-C 'phone will only ever be compatible with one DAC/amp (the one that's built into the cable), it will sound the same no matter what it's plugged into; a 3.5mm 'phone might sound better/different/worse depending on what it's plugged into.
And if you're talking in generalities, I'd still say the 3.5mm are better if for no other reason than that the most expensive USB-C earphone on Amazon costs $150 and gets 3.5 stars, while a quick search shows several $1000 3.5mm earphones that get 5 stars (or pretty close to it). Which isn't to say that more expensive is necessarily better, nor that Amazon reviews are inherently trustworthy, but it's probably a pretty good indication.