I guess I just don't really feel any difference between the two, so what medium it is distributed via seems like an arbitrary categorisation.
For the sake of argument it's not totally arbitrary. Download only titles have a lot less exposure to the casual gaming crowd as they aren't something that are heavily advertised outside of the online stores they are purchased in. Through this thought exercise I've already picked up on a lot of games I will buy/play because I didn't know of or glossed over due to no mass advertising/media review campaign (like TxK). No one size fits all to the situation, but then again this is just for fun so we can call it an arbitrary line and then you can participate or not. No biggie, it was just meant to spark some conversation.