OnePlus 2 vs. OnePlus One: Should I upgrade?

One Plus two is definitely an upgrade over One Plus One. Here is a brief comparison -
Design
One Plus One had a polycarbonate body. The new device feels more classy with the all metal unibody design. It carries a magnesium aluminium alloy frame along with steel accents. Another added feature is the fingerprint scanner.
The One Plus Two weighs a bit heavier than One Plus One ( 160 grams) at 175 grams. The added weight, however, is due to the metal body construction. One Plus Two now supports USB-C charging point in comparison to the microUSB point on One Plus One. Physical dimensions of the new device is 151.8 x 74.9 x 9.9mm compared to 152.9 x 75.9x8.9mm on One Plus One.

Display
One Plus One had a 5.5 inch LCD screen at 1080p resolution. One Plus Two has kept the same resolution, but it now is much brighter with the in-cell IPS LCD display. It has improved sunlight legibility.

Hardware
The Snapdragon 801 processor on One Plus One has been replaced by Snapdragon 810 processor. Being a 64 bit processor it provides better computational ability. However, it could have overheating issues, though One Plus claims it has improved the performace with the use of thermal gel and Graphite. One Plus One came with 3 GB RAM. Now, the new device will have an upped 4 GB RAM for the 64 GB version. 16 GB version will have the same 3 GB RAM.

Camera
One Plus has decided to continue with the same 13 MP camera as on One Plus One. Other added features include Laser Focus and improved Optical image stabilisation.

Battery
The 3100 mAh battery on the older model has been upped to 3300 mAh. One Plus One had a great battery backup. We can expect the same on One Plus Two as well.

My Take
I would treat One Plus Two worth as an upgrade from One Plus One. There ahve been plenty of improvements in the device. I do not think there should be any doubt about the fact the new launch from One Plus will be better than its predecessor.

Specs comparison between OnePlus One and OnePlus 2 smartphones :

OS : Both OnePlus One and OnePlus 2 works on the modified version of Android OS namely CyanogenMod 11S.

Camera : Both OnePlus One and OnePlus 2 have 13 MP primary camera and 5 MP secondary camera.

Memory : Both smartphones have 64 GB internal storage while there is not card slot in either smartphone. OnePlus One has 3 GB RAM whereas OnePlus 2 has 4 GB RAM.

Display : Both smartphones have capacitive touchscreen of 5.5 inches with a resolution of 1080x1920 pixels.

Processor : OnePlus One has a quad-core processor of 2.5 GHz while OnePlus 2 has an octa-core processor of 1.8 GHz.

Connectivity : Both OnePlus One and OnePlus 2 have these connectivity features - WLAN 802.11, Bluetooth, GPS and microUSB.

Battery : OnePlus One has a battery of 3100 mAh capacity whereas OnePlus 2 has s battery of 3300 mAh capacity. Both have non-removable batteries.