The thing I really like about Demo Man is that it feels very unique in its layout. The central shot diverter, the giant looking slings, the captive ball toys and shots to the left are all very unique and you won't find another game that reminds you of Demo Man. Plus the handles are awesome. The only Widebody that plays as fast as a standard body game.
HS2 is a good game, I have nothing against it, but you've had it a while, it's easily replaceable and i don't foresee it ever spiking in value, so you could get another one at a similar price for what you have in your current one probably.