The 500R is 40$ cheaper (approx) and cooler (from the link you sent stats). I also prefer the look of the 500R over the 550D. I think that 550D is pretty boring and featureless visually.
Ive been following the 550D for quite a while now and it does look like a pretty good case for slient freaks. You can have ultra-silent of quite good cooling for it.
I can see from the review that it is well built, but the grey/silver highlights at the top make the whole thing look cheaper. I agree wil Xoil, it looks good for silent freaks as he puts it.