I was really surprised when I took a close look at these two smartphones and realized just how similar they really are, and in so many ways. They are almost identical size and weight, the same size screen and both are Full HD displays, both have 2GB of RAM, they come in 16GB/32GB models (the S4 has a 64GB model, but good luck finding one), and the batteries are only 300 mAh apart. The Galaxy S4 came out in April and the Nexus 5 was just released less than two weeks ago, so the processor in the Samsung Galaxy S4 is showing its age compared to the newer Nexus 5.
Google Nexus 5
The Nexus 5 really shines with its processor, the Qualcomm Snapdragon 800 Quad-Core running at 2.3GHz - the processor d'jour for this years' batch of flagship smartphones, such as the Galaxy Note 3 and the LG G2. It is fast and effective and with 2GB of RAM you will not have any lag in the Nexus 5, especially because its other strong suite is that it is running pure Android 4.4 KitKat, with no skins to slow it down. Android 4.4 KitKat offers many internal improvements for battery life, UI fixes, lower RAM usage, Bluetooth, and much, much more. About the only two bones of contention are the size of the battery and the quality of the camera, although photos so far look promising.
Samsung Galaxy S4
The Samsung Galaxy S4 was their mainstream flagship phone, a position it still holds if the purists will not include the Galaxy Note 3. The processor is old by today's standards - a Qualcomm Snapdragon 600 clocked at 1.9 GHz, or if you are out of the U.S. it uses Samsung's own Exynos Octa-Core clocked at 1.6 GHz. The 13MP camera on the Galaxy S4 was a terrific camera that found its way into the Galaxy Note 3. As is the case with ALL Samsung phones, TouchWiz needs a fresh update, not so much in its menus, but the core programming needs updated to prevent the lag that only takes the 3GB of RAM and Snapdragon 800 processor of the Galaxy Note 3 to run as smooth as it does.
...And the Winner is...Nexus 5
While the Samsung Galaxy S4 is the all-time sales leader in several categories, and was even awarded PC Magazine's "The best Phone on the Planet," a lot has happened since then, namely the Nexus 5 with pure Android 4.4 KitKat. I am a fan of TouchWiz, to a point, but it is an "old and tired" product long overdue for an update and looks especially old when compared to the new 4.4 KitKat. The Galaxy S4 has last year's processor, although many of the other specs are the same - it would probably win in the camera department and does offer the microSD slot, but even the formidable Galaxy S4 is starting to show its age, and is simply outclassed in most categories by the Nexus 5.
Let us know in the comments or on Google+ if you are a Nexus 5 or Galaxy S4 fan, and why!