Using Raid Card rather than Onboard Raid can lower cpu resources, Moreover, moving on raid card.  
Considering PCI Raid Card and PCI-E Raid Card, configuring on raid 0, will the type of the card affect on the transfer performance since PCI-E x1 running at 250MB/s and PCI running at 133MB/s.
 
My options and justifications for either one would be:
PCI: more available slots, cheaper price
 
PCI-E: lower power consumption(haha), more bandwidth?!
 
Last but not least, I would like to save the only PCI-E x1  for futher expansion.
 
If I had made any typos, feel free to correct me.

And also cost. PCIe SATA RAID cards are around 2x(or more) expensive than PCI variant now.

Running RAID 0 on a PCI card would be the equivalent of putting a V-12 in a Kia Rio.
 
It's just stupid.  :-)
 
PCI-e is definitely the better option- price be damned.
 
-mpjesse