1) I need a video in/ HDMI out in a smaller package than the ADV7513/7511, which are QFP (footprint is 12x12mm). The ADV7520 is LFCSP (footprint 9x9), which is just small enough to fit. But I see it is going EOL.
2) I also need only 75MHz data rate support, so again the 7520 looks attractive from a power standpoint (this is important here) as it operates at 80MHz, compared to the 165/225MHz of the ADV7513/7511. I don't have 7520 power numbers, but for the 7513 the data sheet shows around 250mW.
Side note - I would think if you ran the 7513 at 75MHz it would draw less power, but there's nothing in the data sheet that indicates this...
3) I do not need HDCP