The LG Google Nexus 5 and the Motorola Google Nexus 6 were released one year apart, but there is a great difference between their size as well as their specs.
As stated before, the easiest comparison with the Nexus 5 vs. the Nexus 6 is the size. The Nexus 5 measures at 137.9 x 69.2 x 8.6mm (5.43 x 2.72 x 0.34 in) while the Nexus 6 is 159.2 x 82.3 x 10mm (6.27 x 3.27 x 0.40 in). As for the touchscreen, the Nexus 5 is at 4.95 inches while the Nexus 6 is at 5.96 inches. Yes, that is practically 6 inches, which sort of makes this one of those phablets that some users have embraced more in today's smartphone market. The size comparisons are similar to the iPhone 6 (4.7 inches) and the iPhone 6 plus (5.5 inches).
A recent review from Forbes criticizes the upgrade in size, saying that "the best value smartphone on the market [the Nexus 5] has been replaced by the biggest, premium phablet on the market [the Nexus 6]". The Forbes review also went on to say that the Nexus 5 is easier to use one-handed, while the Nexus 6 has a curved back for ergonomics sake. Those who want an AMOLED display should go for the Nexus 6 with a resolution of 1440 x 2550 (493 PPI) while the Nexus 5 has a resolution of 1080 x 1920 pixels (445 PPI).
Of course, those that want the latest in Android are going to want the Nexus 6, since it has the latest with Android 5.0 (Lollipop). Its predecessor can't make the same claim as it still has Android 4.4 (KitKat), but a recent report from ZDnet stated that the Nexus 5 should be receiving the Lollipop update soon.
As for the camera, the Nexus 6 is at 13 Megapixels, and the Nexus 5 is at 8 Megapixels. The camcorder for the Nexus 6 can shoot 4K video at 30 fps with 3840 x 2160, while the Nexus 5 is good for 1920 x 1080 (1080p HD) at 30 fps. The Nexus 6 also has a superior front-facing camera at 2 Megapixels, with the Nexus 5 at 1.3 Megapixels.
As far as what is inside, the Nexus 6 does have the Qualcomm Snapdragon 805 APQ8084 system chip, Quad core 2700 MHz (Krait 450) processor, Adreno 420 graphics processor, 3072 MB RAM in system memory, and 64 GB of built-in storage. The Nexus 5 is similar but inferior in some areas as it has the Qualcomm Snapdragon 800 MSM8974 system chip, Quad core 2260 MHz (Krait 400) processor, Adreno 330 graphics processor, 2048 MB RAM in system memory, and 32 GB of built-in storage.
Let's talk about the battery life. The talk time for the Nexus 6 is 24.00 hours with stand-by of 13.8 days. The Nexus 5 has a talk time of 17 hours with 12.5 days of stand-by. The reason for this is that the Nexus 6 has a 3220 mAh battery while the Nexus 5 is 2300 mAh. Both of the phones have wireless charging built right in.
Much of the other specs revealed on sites like Phone Arena find other features very similar except the Nexus 6 has Bluetooth 4.1 while the Nexus 5 has Bluetooth 4.0. Also, the Nexus 5 is available now, but the Nexus 6 does not yet have a set release date, even though a recent update on PC Advisor says it should be available today.