Rsync has similar issues when you are copying hard links. It has to keep a table of all the inodes/filename pairs it sees so it can detect hard links and relink them on the destination. This can be big if you have a ton of hard links (say in a backup situation).
Rsync at least acts reasonably idempotent, so you can just run it again if it gets interrupted, which is usually why I use it for large copies.
I don't remember off the top of my head if tar handles hard links—it may be inappropriate for this usage.
If you are often restarting rsync jobs or they fail over low speed WAN connections
--partial keep partially transferred files
Is your friend. Esp if you are trying to sync directories with multi GB files. Also if your media is bad or there is a failing piece of network gear along the path
--bwlimit=KBPS limit I/O bandwidth; KBytes per second
Can keep things running smoothly. It even works against disks, I have used it where an array would die if one attempted to read from it too quickly.
Rsync at least acts reasonably idempotent, so you can just run it again if it gets interrupted, which is usually why I use it for large copies.
I don't remember off the top of my head if tar handles hard links—it may be inappropriate for this usage.