Well i'm watercooling with a sabertooth z87, i heard the arc midi r2 is better for that? what case would you go for?
I can't say anything for the Arc midi r2, but I have a R4 and I love it. It's quiet with a ton of room. Really well built, with almost everything except the motherboard tray is removable. The airflow in the case is great as well. Here is a modders prespective on the R4 if you are curious:
I have the arc midi r2 and it's a great case. It comes with three 140mm fans instead of the two. The dust filters also work quite nicely and can be easily removed for cleaning. The side panel window looks nice aswell. If you are going for a sleeker design i'd go with the define r4,but for airflow and better water cooling support the arc midi r2 is the better case.