Onboard Sata II vs PCI Sata II card

I brought a PCI sata card, for an old computer's spare Sata Hard drives.

Since then, about 2years ago, I have taken out the Sata hard drives and currently have them in my main comp.

So, the PCI Sata II card is sat spare atm.

Now, I have a Asus M3A32-WiFi Deluxe motherboard, with 2x WD 74GB Raptors, setup as IDE mode in BIOS and Im using one for Win 7 RC and the other to install programs/games on.

Which is better, the onboard SATA ports or the PCI Sata card?

Both fully support Sata II and I have a spare PCI slot on the motherboard, so thats not a problem.

When Win 7 release is out and about, I will download it (pre-ordered) and plan to format and install fresh, so whilst Im at it, I might as well see if its better to use the PCI card instead of onboard.

Current (main comp) has:

Sata port 1 - WD Raptor 74GB
Sata port 2 - Seagate Barracuda 500GB
Sata port 3 - WD Raptor 74GB
Sata port 4 - Seagate Barracuda 500GB

The motherboard has 6 Sata ports, but the first 4 are controlled by its Southbridge (AMD SB600 chipset). The other 2 ports are as follows:

Sata port 5 - Sata Optical Drive (Samsung Multi DVD with Lightscribe)
Sata port 6 - Sata Optical Drive (Samsung Multi DVD)

According to the motherboard spec/manual, these last two connectors are controlled by the onboard Marvell 6121 and 6111 Pata and Sata controller.

I dont plan to RAID anything, as I have already experimented with RAID with this board, got results and happy with leaving setup as IDE mode.

When I purchased the PCI card, it came retail packaged with a CD, which I cannot find, so from the details found on the actual card itself:
Sata2000D
Sata2100
Ver 1.3

Initio INIC-1622TA2

E119801

Googling around, it looks like I can only find specs stating its Sata I (1.5Gb/s) not SATA II (3.0Gb/s).

Which is better the onboard or the PCI?

Is there anyway I can find out without installing it?

PS - I cant afford to spend anything atm, so no replacing Hard drives etc...