RAID, as applies to consumer RAID anyway, has always been a bit controversial. If you Google about a bit, you will find everything from scholarly works to outright flame wars. lol
Personally, I am not a big fan of software RAID of any kind. An explanation is probably in order. A true Hardware RAID array, I am defining as a storage system that is seen as a black box by the operating system. It provides its' own processor, catching, disk syncing, etc. It accepts data at buss speed and gives back data at that speed. It represents no additional cpu load or memory catching load to the host system.
Anything less is some form of software or fake RAID. Anything from slightly assisted to completely implemented in user software.
I would willingly defer to your greater knowledge of how fake RAID is implemented in Windows. Since Windows is proprietary, I am not sure anybody outside Microsoft really knows exactly how it is being done. My knowledge in this area is severely limited for sure.
Having said that, I do know there is program code in non-volatile memory, firm ware, that must be run by the Windows kernel on the cpu to help implement the RAID. Most of these RAID systems also use at least some main memory for catching purposes too. This same scenario exists for any other OS also. The hardware just isn't there to do a complete implementation without main system help.
As I have mentioned before, if you have plenty of spare cpu cycles and lots of memory to work with, you can indeed get some improvement in overall system speed. If you aren't careful though, you can wind up fooling yourself. Remember, a chain is only as strong as its' weakest link. If you are looking at disk through put on an otherwise unloaded Windows system, which is the way most of these benchmarks are done, you will indeed see a tremendous improvement. If on the other hand you load the system up with running processes, as it would be in a normal use situation, you may still see some improvement in disk through put but you will be slowing everything else down to get it. You can see the same phenomena on other OSs to one extent or another too.
Linux's memory and cpu task management, especially in the later kernels is, with out doubt, better than Windows. I have no empirical data to back this up, but I suspect that in most cases, a reasonable fast SATA drive that is properly optimized with hdparm would make for a system that is just as fast if not faster over a wide rage of loads than any of the fake RAID setups. The complexity of a system without fake RAID is also reduced, which almost always translates to, more robust and reliable over time.
Below is a Link that will probably either give you more info. than you really wanted, or link you to same. http://linuxmafia.com/faq/Hardware/sata.html