FurMark Stress Testing

[willxinc]

I recently bought a MSI GTX 980 GAming 4G and have been overclocking it with MSI Afterburner.
To test its stability, I was using FurMark. I noticed that while using FurMark, the voltage would not goto its limit, and a result, a lower clock was used for the stress test. 
This can be avoided by running another GPU intensive application (such as GPU-Z's PCI-E stres test) at the same time. This results in lower FPS in both applications, but still results in 100% load, but this time at the correct max Voltage and clock settings.
 
I was wondering if there were any downsides to testing stability this way. I also keep seeing people telling others not to use FurMark, if not, what are some good alternatives and why?
 
On a sidenote these are the settings I'm currently at using a custom self-modified bios:

Core: +156 MHz (1522 MHz total)

Mem: +312 MHz (3815 MHz total)

Temp Average / Max: 70C @50% Fan Speed

[gozzygozborn]

Running two benchmark applications at the same time would mean neither benchmarks are accurate. You could use unigine as an alternative to furmark.

[willxinc]

I'm not trying to benchmark, I'm trying to stress test the card. Obviously neither are accurate, but it should be enough for a stress test right?

From the quick glance I have Unigine, the free version doesn't seem to have a looping mode for stress testing or an I wrong?