The Signet of the Fifth Circle is certainly better for shadow unless you are not hit capped and need all of the 162 hit. If you only need about 60 hit I would go for the Signet and reforge some of the mastery to spirit.
Keep Signet of the Fifth. The Heroic version which comes from Shannox is quite easily obtainable these days with how easy entry level bosses are in new instances. Wait for heroic
Okay so Signet of the Fifth Circle does not come from shannox. Its a ring from heroic Cho'gall. So im not quiet sure what you are talking about. Anyways both rings from Shannox (normal and heroic) would be an upgrade for you.
And while most cases higher ilvl is usually better, since they are so close in level the secondary stats are important. And haste is such a good stat for shadow.
My advice though is take a look at your stats, weight out your personal stats and what will actually benefit you more. If you're at the haste "soft cap" you can go with the cystalline. Now as far as being over hit with the crystalline you can always reforge out of hit from other places. If you provide an armory link it would help to make a better opinion other than hey these 2 rings yadda yadda yadda
Not to hijack, but I have a ring problem here too. Hopefully easily answered, because it's bugging me....
Crystalline Brimstone Ring vs Soothing Brimstone Ring.
Most BiS lists for shadow say Soothing, askmrrobot says Crystalline;
and simcraft rates me reforged with Crystalline at 24811dps versus Soothing at 24843dps
Is there a right answer? Or does it matter?
It won't let me link yet, but my character is Firiona on Malygos-US(H)
Thank you for your help, and thanks for starting this semi-relevant topic OP
As far as I know Simcraft runs a (big) number of simulations, each with different results, and then posts the average result to you. This means that if you run the simulations again you'll probably get a slightly different result. But as you can see the 2 rings are not far from each other in the end result.
Personally I took the hit+mastery ring, because I like mastery more than crit. I considered the crit+spirit because of my healing offspec too... so I actually bought them both ;-)