Linux software raid is better then fakeraid.
Realise that with 'fakeraid' what is happenning is that your emulating hardware functions on your main CPU. It's very similar to the difference between a software modem or a Winmodem versus a 'real' serial modem. In those cases you using stripped down hardware that provides a interface for the software emulation.
Effectively with fakeraid your using software raid, but instead of using what is provided by your OS vendor your using drivers to run software raid. This works great in Windows-desktop-land were Microsoft has disabled the software raid functions in their desktop OSes, but in Linux you don't have that limitation.
When you compare the fakeraid drivers provided by the hardware manufacturers versus the Linux built-in software raid the Linux software raid is superior in quality, performance, and capabilities. It's faster, it's more widely used, massively tested, people have reviewed the source code over and over and over again and has proven itself over the years. Fakeraid drivers are proprietary, generally worse quality, and generally perform badly.
For server stuff it's a way that hardware vendors can sell you 'RAID' without actually having to actually provide it.
It's actually faster then hardware raid if you want to get down to it. There are a few benchmarks here and there and always show Linux MD raid as competitive with hardware raid. Most people think of 3d performance with video cards when they think of hardware vs software... but video cards are unique. With hardware raid your using generic intel or risc cpus running at a few hundred mhz. Software raid with a low-end Intel cpu running at 2ghz absolutely stomps all over them.
That's not to say that Linux MD is better then hardware raid. What you want to use depends heavily on budget, size of the array, recovery features, cache, PCI bus bandwidth and other such factors. Hardware raid is certainly desirable... there are a lot of things that expensive hardware raid controllers can do to help a busy server and protect data that software raid just can't do yet.
But this is why it's difficult to use fakeraid in Linux sometimes. The developers know that software raid is better and given a choice this is what you want to use 95% of the time when you have to make a choice. faster, more stable, safer, etc
Sometimes fakeraid can have some sort of limited acceleration for some things... but it's probably not worth it to bother with that sort of thing much.
About the only time when you want to bother with fakeraid stuff in Linux is so you can get compatability with Windows using the fakeraid on the same machine when dual booting. That's when it's actually usefull.
This page is quite usefull for this sort of stuff...
http://linuxmafia.com/faq/Hardware/sata.html
Here is a classic benchmark were Linux MD stomps all over 3ware raid card. With some functions the software raid is more then twice as fast.
(remember their are still lots of advantages of hardware raid other then speed. On higher end stuff hardware raid is still going to be faster and more desirable.. talking about SAN sort of things especially... so don't get me wrong)
http://spamaps.org/raidtests.php