Overall bandwidth is what matters performance-wise.
Anyhow, which version of the 3050 are you talking about? Most of those (specially the mobile ones) are all sub 200GB/s. AFAIK there's no model that does the number you mentioned, and only the 3050 8gb desktop goes past the 200GB/s mark at the same 128bit bus, but still slower than those 256GB/s you mentioned.
Many of the laptops ones are even 96-bit lol
I'm not arguing against the 5060 being way faster, it's just that being faster but not having enough vram to run your task makes it useless at it, no matter how fast it is (reminder that we're not talking about games here).