You really should just read the specs on each carefully, I see the Decklink card as capable of cross conversion of HD formats, while I believe the Kona can do full blown upconversion. Don’t know if you need that, but Blackmagic make great products, I’ve owned both, and I prefer AJA products. The support is unbelievable. Plus, the HDMI scheme on the BM card is ridiculous, takes up an extra slot FCOL.
Have a wonderful day.