Big thing to also take from that article is that the POWER8 uses over 2 times as much power as the Xeon E5 v4. Depending on the use case this can be very important.
If single-threaded performance or memory bandwidth is more important to your use case then POWER8 would steamroll a Xeon E5 v4 even factoring in the power usage, I'm actually looking at trying to get a S812LC at work to eval moving one of our very heavy transactional PostgreSQL databases to for this very reason (having to run a seq scan over a 80GB table would benefit heavily from the increased memory bandwidth).
As per article linked by the OP, the single threaded performance of the POWER8 is 87% of the Intel CPU at the same clock [1].
The per-core performance is higher thanks to the 8 thread SMT capability of POWER8 (although the sweet spot is normally 4) and its massive 8-way execution. So POWER8 is excellent for heavily threaded applications, but for pure single thread speed, Intel is still king.
[1] IIRC POWER8 and Intel CPUs peak at around the same clock speed.
