While none of these smartphones (Nexus 5 (2015) and iPhone6S) already exist physically, these days we are knowing some important details about both (as Cortana for Android or System UI Tuner), which will allow us to look as far as performance is concerned.
Design
Here we enter a new field, odd, since it seems Google has confirmed the existence of two Nexus, one manufactured by LG and other by Huawei. So, these two versions would have different designs, and it can be a little bit weird. In the case of Huawei terminal, we can expect a good design, according to what we're seeing lately in the range of Chinese manufacturer. Whether they go in the direction of Huawei P8 as in Honor 6, both styles would be a success.
Version manufactured by LG would be smaller than Huawei. The return of South Korean manufacturer could be connected with the fact that both the Nexus 4 and the Nexus 5 were two indisputable successes, something that has not been continued by the Nexus 6. The Nexus manufactured by LG would have a simple design and finishes.
Following these same sources, the Huawei Nexus would be made with some material nearer to a metal finish, as seen in the Huawei P8; and Nexus by LG would be made of plastic.
According to a video posted in May, iPhone S6 will be a redefinition of the current model with some modifications that have been analyzed by some experts. The first impression is of a rather sober and perhaps overly continuity phone.
Display
The Nexus manufactured by LG would have 5.2 inches and with Huawei it would be a 5.7 inches screen of 2K, as it appears.
Analysts point to an iPhone with Force Touch on the screen. The technology, which has appeared in the new MacBook and MacBook Pro screen with Retina 13 running as protagonist in Apple, which however will have a slightly different implementation that has the component of these laptops. Instead of the pressure exerted by the fingers on the screen of the iPhone it will be a coat detected that monitor the contact area to determine how much pressure is applied. That layer will use capacitive technology and a flexible integrated circuit (FPC) which will save thickness.
Many details are unknown, but indications are that the current two sizes of 4.7 and 5.5 inches will remain, as the rumor of a sapphire display, but there are also sources that speak of a screen that will offer the 3D experience without special glasses.
Cameras
This information is still unknown.
Software/Hardware
From WCCF Tech we get some pictures where we can see a couple of screenshots with the position of this Nexus 5 (2015) in AnTuTu Benchmark, which comes to 85 530 points. Recall that the Meizu MX4 obtained an average of 47 765 points and the Galaxy S6 68 157 points this year. This could be due to bring a Snapdragon 820 processor, the same one that could bring Xiaomi MI5 and HTC Aero.
Also are speculating that this new generation of Nexus 5 is the output of a new version of the operating system. Do not forget that everything points to Android M, that was presented during Google I/O 2015 and therefore may be in late summer and be ready for presentation.
The next iPhone would come equipped with RAM LPDDR4, which offers increased speed and optimum performance, no matter how many apps are used at the same time. On the amount, there is no number, but it should be 2 GB of RAM, twice what they have in current models.
As for the processor, it would be an A9, produced jointly by Apple and Samsung and that among their qualities, it would take lower energy consumption and a significant increase in power.
Of course, it would come with iOS 9.
Autonomy
For 5.2-inch Nexus manufactured by LG they are considering a battery with 2,700 mAh. Huawei Nexus of 5.7-inch will have a 3,500 mAh battery. It would have a better optimization of battery thanks to Android M Doze feature.
This information is unknown but it has been told that iOS 9 would offer a more efficient optimization of processes, including those running in the background, increasing the battery life of iPhone 6S.