Vivo x21 was hyped for its in-display fingerprint sensor, while the Oneplus 6 was hyped about its great specs as oneplus is a smartphone brand that launches only 2 smartphones a year(really great when compared to the innumerable phones that Xiaomi releases every year!) and both of which will come with the flagship level specs available at that time in the market. Lets quickly compare the Vivo x21 with the Oneplus 6.
Display: Both devices come with a 6.28-inch FHD+ display with an aspect ratio of 19:9(instead of the usual 18:9 because of the notch present in the top of the screen). The Vivo x21 has a super AMOLED display, while the oneplus 6 has an Optic AMOLED display. Under the AMOLED panel of Vivo x21, we get an in-display fingerprint sensor.
Camera: The Vivo X21 packs a 12MP(f/1.8)+5MP (f/2.4) camera setup and in the front, we get a 12MP(f/2.0) along with 3D mapping technology for face unlock. While the oneplus 6 comes with a 16MP+20MP(f/1.7) dual camera setup equipped with OIS, EIS, and dual LED flash, and for selfies, we get a 16MP(f/2.0) camera. A simple camera comparison between these 2 devices proves that the Oneplus 6 is the clear leader here.
Processor and storage: Well this is where I lost all my hopes for the Vivo X21. Oneplus 6 is powered with the latest Qualcomm Snapdragon 845 SoC clocked at 2.8Ghz and the GPU is the Adreno 630. It comes with 6/8 GB of LPDDR4X ram, and 64/128/256GB of internal storage. Looking at this flagship level specs, it is really disappointing when you hear about the specs of Vivo X21: It is powered by Snapdragon 660 SoC coupled with Adreno 512GPU and comes with just one variant: 6GB ram+128GB internal storage. Of course, the Snapdragon 660 is not a weak processor, but it is really not a strong processor when compared to the powerful Snapdragon 845. So here too Oneplus takes the lead.
Software and Battery: The vivo x21 comes with a FunTouch OS 4.0 running on top of Android 8.1 Oreo. It has a battery capacity of 3200mAh. The Oneplus 6 comes with OxygenOs 5.1 on top of Android 8.1 Oreo and comes with a battery capacity of 3300mAh along with the support for the company's famous Dash Charge technology. Both phones have an Android P beta build available for download.
Price: The 6GB+128GB storage variant of Vivo x21 cost Rs. 35,990. The Oneplus 6 comes with 3 variants: 6GB+64Gb-Rs.34.999, 8GB+128GB-Rs.39,999, and an avengers limited edition version:8GB+256GB priced at Rs.44,999.
Verdict: Even though Vivo x21 came with some spectacular new technologies, it has failed to impress me in terms of specs and camera, when compared to the Oneplus 6. However, it's great to see that smartphone companies are trying to bring some new innovation to smartphones(Talking about new innovation by smartphone companies, Techulator has a great article about the new Vivo NEX which introduced a new way to remove the notch! Check out the article here: http://www.techulator.com/resources/ViewResource.aspx?ResourceId=17351 )
But for me, Oneplus 6 remains the winner in this comparison.
Note: I have only covered the major differences here, and I have exempted other small things like connectivity options, expandable storage, glass protection etc.
Regards,
Deepak Mathews Koshy