These are both great case and I am not sure what to use to replace my current case. I plan on using a h100i in the future. With that in mind the 500r has more clearence and has more fans included with the case.
Fractal R4
Another vote for R4!
R4
It's all up to you because you're going to be looking at it for as long as you keep it.
I like both cases the R4 does have better cooling, but i don't like its width
I would go with the R4 but better clearence is good if you are gonna be doing water cooling and all that fancy stuff :)
I like the fractal cases. They also look more professional to majority of the time.
I've decided to go with the fractial arc midi r2 because it has more clearence then the r4.
http://www.newegg.com/Product/Product.aspx?Item=N82E16811352031