Well the Obsidian is a case of 180 Dollars, the R4 cost 120 Dollars as much. The comparison is not fair, and it really depends of the hardware you're getting. If you like the Fractal is a great case also, has great cooling and it's a silent case. You can get the fractal and upgrade something.
Well CM sickle flow are just great.
they are different cases, one is possibly more angled towards quietness, and in a different price bracket, figure out your requirements and you'll have a better idea of which one is right for you.
Well i have them in my case and they are not. I cant hear them on night and thats important. though they cant compare with the Vortex.
The led is very nice and they do move a lot of air .