I wouldn't trust any motherboard so-called RAID support. It's generally just half-hearted silicon implementation with mostly software RAID drivers sitting on top of it. Plus, if your motherboard dies, it's chancy if you can recover the array. If you stick with full software RAID (such as what Windows provides) it's much more portable and you have pretty good odds of recovering an array through a mobo/controller failure. Plus, you've got plenty of cores & CPU horsepower these days to make the amount of CPU overhead not really worth acknowledging.
Now if you've got a high-quality 3rd party RAID card with battery-backed RAM, that might be worthwhile. But probably not for what you need.
Personally, I want bonded 10GbE to a NAS with 10-12 disks running FreeBSD with ZFS 0+1 that has 64GB of RAM for the ZFS cache.