Here's an interesting find I came across while I was looking for an easy way to compare gear sets (mainly the effect gems have on AP/crit).
Link.
On there you'll be able to see the difference between two gear sets, the set with RED and the set with SSD.
What you'll see is that RED gives 3% crit damage and 0.17% crit versus the SSD's 41 AP.
In the end, I think RED is better. It costs a lot more, but I think it'll be worth it.