I did think about it. Before I posted I spent more than just a small bit of effort. I still don't see what the difference actually is though. Yes I know what "but" means. I know all those words... but...

I do not see any actual difference. Anything you apply those two descriptions to are both "off-topic" as well as "interesting", according to those descriptions. The "but" does not make any difference at all as far as I can see. The other replies say there is a preference implied (I already knew that that was the intention), but as I just wrote, however you parse it, you end up with both attributes and I don't see any preference actually being applied. I see the attempt, yes, but I don't see that there is any effect.