I have both, the Io and a Kona3. To me the issue is how may computers do you need to capture on or if you have a laptop. I got the Io to do ETT and capture offsite and I was tired of packing up my Quad G5. So now I just take my MBP and the Io to capture or master, works great. I also started doing HD to SD downconverts from Kona3 to Io.
If I only had one computer I would probably with the pci card, if I needed more flexibility the Io is great. If you go with the Io you can add Fireward ports to your desktop, they are cheap. Also DVCProHD can be captured over Firewire. The good thing is they both work great.
Io gives you flexibility
Card gives you HD (also acceleration DVCProHD, RT and HDV)
BTW I was going to get a Blackmagic card before I decided to get the Kona3, so glad I did, a much better card. The LH is a great card also if you don’t need upconvert.