The upper roof holds the snow longer because it's colder upstairs.
We also get some nice icicles form as the snow melts.
It's a nice framing effect from our bedroom window upstairs.
The snow that sheds off the roof is hard to clear--it's compacted, heavy, sticky, and often has large chunks of ice in it.
Chunk by chuck, the snow sheds off (and it's really heavy and nasty stuff to clear).