Dual xeon or i7 980x

what apps in specific?

3ds max , maya and other multi threaded apps for heavy rendering

id say definitely dual xeon.

I don't know - the extra clockspeed could tip it in favor of the 980x, which will also probably have lower power consumption.

I've buyed an i7 980x and i'm extremely content with it.
Win-Mark (Microsoft Win 7 64Bit, Scale from/to 1.0-7.9): 7.8 7.8 7.9 7.9 7.7
System: 1 x 980x, 24GB Ram, GeneIII, GTX480
Nor Dual Xeon-System will do that