On the other hand, dnf/yum downloads repos and packages in parallel while zypper still does everything one at a time, which means every kilobyte-sized package t

On the other hand, dnf/yum downloads repos and packages in parallel while zypper still does everything one at a time, which means every kilobyte-sized package takes a second or two each to download, from setting up and tearing down a new TCP connection each time. It's especially annoying in Tumbleweed because rolling distro == lots of tiny packages updates all the time.