Another factor that people forget with FakeRAID until it is too late... if your OS crashes your RAID is useless. With hardware RAID you can rebuild your RAID after a drive loss even when the system is offline. The datacenter people don't need to know if the OS is healthy, if it is on, etc. They can swap drives and let the RAID controller repair the array.
With FakeRAID there is no RAID until the OS works and is healthy. So even if you replace a drive, the array might be unable to repair itself.
Dealing with someone facing this problem right now. System crashed with the RAID array lost a drive and won't boot. Not the OS is having issues and there is no RAID at all.