Comment by cryptonector

> GC gives lets you have garbage cycles. RC does not.

This is the biggest difference, but if you disallow cycles then they come close. For example, the jq programming language disallows cycles, therefore you could implement it with RC or GC and there would be no observable difference except "eager destruction", but since you could schedule destruction to avoid long pauses when destroying large object piles, even that need not be a difference. But of course this is a trick: disallowing cycles is not a generic solution.