[tw04]

Copy-on-write filesystems are inherently better for flash media because they never overwrite in place. They always allocate a new block and mark the "old" block freed when it is no longer referenced by the active filesystem (or snapshots if supported).

Flash Media HATES overwriting data in place because it requires the block to be freed, then re-written.

Now, modern flash firmware tries its best to allocate new blocks anyway, so some of it is a wash, but it is overall a better way to write to flash media.