To answer this we used the Geekbench and Sunspider benchmark tools. Geekbench tests integer, floating point and memory performance to create single-core and multi-core performance scores.
Sunspider uses JavaScript to run a number of browser-based tests several times to determine the speed of the browser and processor. With Geekbench a higher score is better, while with Sunspider a lower score is better.
In our tests the iPhone 6 Plus had an impressive 1,619 single-core and 2,920 multi-core score on Geekbench and 350.0ms on Sunspider.
The Nexus 6 had 1,053 single-core and 3,178 multi-core scores on Geekbench and a 794.2ms on Sunspider.
With real world use we found that, for general purposes, both phones are very fast and will meet most users' needs. However, with prolonged use there are a few factors that tip the performance section in the iPhone's favour.
With extended use we noticed that the iPhone 6 was at times faster when it came to web browsing, and definitely performed better with demanding tasks such as 3D gaming. In these situations the Nexus 6 can begin to slow down and heat up.
Winner: iPhone 6 Plus
Camera
Imaging performance is one area in which Apple and Google have failed to impress in recent years, and both companies have attempted to rectify the situation with their latest offerings.
Apple has loaded the iPhone 6 Plus with an advanced 8MP with Optical Image Stabilisation (OIS) rear and 1.2 Facetime front camera. Google has equipped the Nexus 6 with 13MP with dual LED ring flash and OIS rear and 2MP front cameras.
Testing the two rear cameras we found that both had their strengths and weaknesses.
In regular lighting conditions - when viewed on a display other than the Nexus 6's oversaturated screen - images shot on the Google-phone were crisper and generally featured more realistic colours than those on the iPhone 6 Plus.
White balance levels on the Nexus 6 were also more realistic, and the Google phone's ring flash component performed better than the iPhone 6 Plus dual-LED flash.
Dual-LED flash is designed to apply exactly the right colour combination to your photo's subject to create more consistent levels.
The Nexus 6 ring flash created more consistent shots when shooting in low light for a more diverse collection of subject matter than the iPhone 6 Plus could produce.
The combination of factors mean that, for general purposes, the Nexus 6 camera has a lead on that of the iPhone 6 Plus.
That said, turning the flash components off we found that the iPhone 6 Plus performed better in dim conditions. This is interesting as both handsets come with OIS components.
OIS reduces light alterations and degradations on images captured in low light
by compensating in real time for shaking and vibrating while shooting.
The iPhone 6 Plus also boasts slightly faster shutter speeds than the Nexus 6, and is able to capture images a fraction of a second faster than its Google competitor.