| Hardware and OS | Vivo X21s | Oppo A3s |
| Operating system | Funtouch 4.5 OS (Android 8.1 Oreo) | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | 4x 2.2 GHz Kryo 260, 4x 1.84 GHz Kryo 260, Cores: 8 | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | Qualcomm Adreno 512 | Adreno 506 |
| RAM | 6 GB, 1866 MHz | |
| Internal memory | | 16 GB, 2 GB RAM |
| Internal Storage | 128 GB | |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| Memory Card Slot | microSD, microSDHC, microSDXC | |
| User Interface | Yes | |
| Display | Vivo X21s | Oppo A3s |
| Type | Super AMOLED | IPS LCD |
| Size | 6.41 inches | 6.2" inc |
| Resolution | 1080 x 2340 pixels | 720 x 1520 px |
| Touchscreen | Yes | capacitive touchscreen |
| Screen-to-Body Ratio | | 81.2% |
| Display area | | 95.9 cm2 |
| Display aspect ratio | | 19:9 (height:width) |
| Pixel Density | 402 ppi | 271 PPI |
| Protection | Corning Gorilla Glass 3 | |
| Colors | 16M | 16M |
| Features | Capacitive, Multi-touch, Scratch resistant | |
| Connectivity | Vivo X21s | Oppo A3s |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| 4G Network | Yes | LTE |
| Wi-Fi | a, b, g, n, n 5GHz, ac, Dual band, Wi-Fi Hotspot, Wi-Fi Direct | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| NFC | No | |
| Network | | GSM / HSPA / LTE |
| SIM card | | Dual SIM (Nano-SIM, dual stand-by) |
| Bluetooth | | 4.2, A2DP, LE |
| SIM | Nano SIM | |
| Edge | | Yes |
| Dual SIM | Nano-SIM, Nano-SIM / microSD | |
| GPRS | | Yes |
| Wireless Charging | No | |
| GPS | GPS, A-GPS, GLONASS, BeiDou | Yes, with A-GPS |
| Speed | LTE 850 MHz LTE 900 MHz LTE 1700/2100 MHz LTE 1800 MHz LTE 1900 MHz LTE 2100 MHz LTE 2600 MHz LTE-TDD 1900 MHz (B39) LTE-TDD 2300 MHz (B40) LTE-TDD 2500 MHz (B41) LTE-TDD 2600 MHz (B38) | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | 2.0, Micro USB | microUSB 2.0, USB On-The-Go |
| Camera | Vivo X21s | Oppo A3s |
| Image | 4032 x 3024 pixels | |
| Main camera | 12.19 MP (megapixels) | 13 MP, Dual |
| Specs | | 13 MP, f/2.2, AF
-2 MP, f/2.4, depth sensor |
| Features | LED | LED flash, HDR, panorama |
| Video | | 1080p@30fps |
| Selfie camera | 24.84 MP (megapixels) | 8 MP, Single |
| Multimedia | Vivo X21s | Oppo A3s |
| Loudspeaker | Yes | |
| Handsfree | Yes | |
| Video Out | Yes | |
| Ring Tones | Yes | |
| 3.5 mm Jack | yes | Yes |
| Radio | Yes | FM radio |
| Design | Vivo X21s | Oppo A3s |
| Colors | | Red, Dark Purple |
| Waterproof | No | |
| Dimensions | 75.08 x 157.9 x 7.9 mm | 156.2 x 75.6 x 8.2 mm |
| Weight | 156 g | 168 g |
| Battery | Vivo X21s | Oppo A3s |
| Capacity | 3330 mAh, Li-Polymer | |
| Battery capacity | | 4230 mAh, Non-removable Li-Ion |
| Other | Vivo X21s | Oppo A3s |
| Release date | | 2018, July |
| Sensors | Proximity, Light, Accelerometer, Compass, Gyroscope, Fingerprint | Accelerometer, proximity, compass |
