compilation times seem to be close enough to not care about between different filesystems. (ext4, btrfs with lzo compression, zfs with lz4 compression)
boot times don't really matter too. what seems to matter, is how much it slows your system down when doing lots of io, where btrfs either has bugs or compression overheads.
On disk compression results in improved performance and less space used.
Snapshots mean you could snapshot your system before you let your mom on the computer and after she pollutes your browser history with pinterest, aol email and browser toolbars, you could restore back to the snapshot.
You can also use snapshots to restore computer after a hardware failure. I needed to rebuild the zfs pool on my desktop a while back to switch drive layout and to back it up I did a zfs send/recv to my nas, rebuilt the pool and then zfs send/recv back to the desktop to restore my exact system.
Then checksums ensures that everything is perfectly preserved. In some cases it can give you an early warning that a drive is dying and in others, it can prevent movies/pictures of loved ones from corrupting.
Then, folder mount points on ZFS also make for extremely easy migration from distro to distro. As an example of this, You can install a secondary OS alongside another and switch from one to the other while maintaining all files from the old install without juggling partitions. Just leave entire drive as ZFS:
zfs create pool/OS -o mountpoint=none
zfs create pool/OS/Arch -o mountpoint=/
zfs set mountpoint=/pool pool
zpool set bootfs=pool/OS/Arch pool
Then lets say you didn't like arch and wanted to use gentoo instead. All you would have to do is:
zfs set mountpoint=/backup pool/OS/Arch
zfs create pool/OS/Gentoo -o mountpoint=/
zpool set bootfs=pool/OS/Gentoo pool
This would switch your install to Gentoo while keeping your entire arch install intact. You could switch back if needed or copy the needed files over and then delete it. You could also do this with your home directory to just directly mount your arch home directory into your gentoo install in the exact same spot without needing to copy files over.
Also, in regards to your performance concern, a ZFS raid on more than 2 disks (e.g. a raid 5,6,10) outperforms ext4 + mdadm in virtually all cases, zfs also outperforms ext4 + mdadm on a raid 1/0 in multiuser configs (like a server serving files to 5+ clients at once). And that is in just a basic, no frills configuration. With ZFS, you can turn on compression and add SSD caches to make that even faster.