From what I have found all of the DS3(x) boards are the same from a chipset point of view, except that they differ in features a little. For example the DS3 doesn't have SATA Raid while DS3R does, DS3P has extra PCIe slot and -1 PCI slot. Some have FW, some don't. I think the DS3L has half of the Sata ports missing (L for light?).
What you could do is go to a site like Scan and select all of the P35 boards (I did it for you,
here), then click compare. This is what I am doing currently, trying to decide on a DS3 board for a Q6600. I think I will go with the DS3R (although apparently Sata Raid does not currently work so it may be a moot point).
Warning: There are different versions of photos of these boards on different websites. I have seen the same board being shown with rear mounted LPT ports, and some without (they have more rear USB ports instead). I think it's a difference between V1 and V2 boards. I haven't gotten to the bottom of this yet.
BTW - I'm currently downloading and examining all of the manuals for each of these boards from Gigabyte. That should clear stuff up a bit.
Edit: I have just noticed that the DS3L boards have the ALC888 audio chip, rather than the ALC889A of the others. May be no big deal?