If yr a radio playlister or researcher your main desire is to stop people switching over: a lot of people stick to a single radio station and don't channel hop much so if someone switches over or off you might not get them back for a while. Video channels are far more accepting of switching, because TV users channel hop more.
So imagine songs being scored on a scale of 1 to 5, with 1 meaning "awful, would switch off/over", 5 meaning "terrific, would stop channel-hopping if I found it", and 2-4 being various degrees of like/dislike which cause no immediate behavioural reaction. Obviously you want the songs on your playlist to have as high an average score among your listeners as possible. But on radio you want to minimise the 1-scorers, and on video channels you want to maximise the 5 scorers. If a song like Aly and AJ has 2/3 "5" and 1/3 "1" reactions, it will have a higher average score than a song with all "3"s but will be a much bigger risk for a radio station.
And I think Aly & AJ IS that kind of song - the way it starts so breathlessly, it's in-yr-face with its poppiness and if you dislike teenpop in general I'd guess you'll find that less palatable than "Gimme More" or "About You Now". So even beyond the demographics there's a reason why it might hit on video and not radio.
Speaking of demographics, I guess Radio 1 and other stations must have a very firm idea about what age people start listening to radio regularly, and I would imagine that average age is getting nearer and nearer to the age they start driving. I get the impression that Radio 1 has basically given up on yr actual kids, which makes them much less likely to take a chance on something with kid appeal.