The -63 in proposed has other prerequisites for SR-IOV in Azure: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1650059 and https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1657540
Since -64 is newer, and going GA on Monday I hope, it's best to go with that one.
The -63 in proposed has other prerequisites for SR-IOV in Azure: https:/ /bugs.launchpad .net/ubuntu/ +source/ linux/+ bug/1650059 and https:/ /bugs.launchpad .net/ubuntu/ +source/ linux/+ bug/1657540
Since -64 is newer, and going GA on Monday I hope, it's best to go with that one.