| Hardware and OS | Vivo Y66i | Oppo A3s |
| Operating system | Android 7.1 Nougat OS | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | Quad-Core 1.4GHz ARM Cortex A53 CPU Clock | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | Qualcomm Adreno 308, 500MHz | Adreno 506 |
| RAM | 3GB | |
| Internal memory | | 16 GB, 2 GB RAM |
| Internal Storage | 32GB | |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| Memory Card Slot | microSD, microSDHC, microSDXC | |
| User Interface | Yes with Funtouch OS 3.2 | |
| Display | Vivo Y66i | Oppo A3s |
| Type | IPS, LCD capacitive touchscreen | IPS LCD |
| Size | 5.5 inches HD | 6.2" inc |
| Resolution | 1280 x 720 Pixels, 24 bit color depth | 720 x 1520 px |
| Touchscreen | Yes Multi Touch Support | capacitive touchscreen |
| Screen-to-Body Ratio | | 81.2% |
| Display area | | 95.9 cm2 |
| Display aspect ratio | | 19:9 (height:width) |
| Pixel Density | ~ 267 ppi | 271 PPI |
| Protection | Yes | |
| Colors | 16M Colors | 16M |
| Features | IPS, HD Display, ~ 267 PPI Pixel Density, Capacitive Multi-touch, Scratch Resistant, 2.5D Curved Glass Screen | |
| Connectivity | Vivo Y66i | Oppo A3s |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| 4G Network | LTE : 850/ 1800 / 2100 MHz, LTE-TDD : 1900 MHz (Band 39), LTE-TDD : 2300 MHz (Band 40), LTE-TDD : 2500 MHz (Band 41), LTE-TDD : 2600 MHz (Band 38) | LTE |
| Wi-Fi | Wi-Fi 802.11 b/g/n, Wi-Fi Direct, Wi-Fi HotSpot | 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 | Standard SIM | |
| Edge | | Yes |
| Dual SIM | (Nano-SIM, Nano-SIM), Dual Standby | |
| GPRS | | Yes |
| GPS | Yes, with GPS, A-GPS | Yes, with A-GPS |
| Speed | LTE Cat-4 150 Mbps Download, 50 Mbps Upload, HSUPA 5.76 Mbps Upload, HSDPA 21 Mbps Download, EV-DO Rev.A 1.8 Mbps Upload, 3.1 Mbps Download | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | Micro USBv2.0 with Charging and Mass Storage Function | microUSB 2.0, USB On-The-Go |
| Camera | Vivo Y66i | Oppo A3s |
| Image | 4160 x 3120 Pixels | |
| Main camera | 13 Megapixels with Single-LED and AF Rear Camera | 13 MP, Dual |
| Specs | | 13 MP, f/2.2, AF
-2 MP, f/2.4, depth sensor |
| Features | Yes with Single-LED Flash | LED flash, HDR, panorama |
| Video | | 1080p@30fps |
| Selfie camera | 5 Megapixel Front Camera | 8 MP, Single |
| Multimedia | Vivo Y66i | Oppo A3s |
| Loudspeaker | Yes with Single Speaker | |
| Video Playback | Up to 7.5 Hours | |
| Video Out | Yes With Wireless Media Link | |
| Ring Tones | AAC, WAV ringtones | |
| 3.5 mm Jack | yes | Yes |
| Radio | Yes | FM radio |
| Design | Vivo Y66i | Oppo A3s |
| Colors | | Red, Dark Purple |
| Dimensions | 6.04 in x 2.98 in x 0.29 in | 156.2 x 75.6 x 8.2 mm |
| Weight | 157 Grams (With Battery) | 168 g |
| Battery | Vivo Y66i | Oppo A3s |
| Capacity | 3,000 mAh | |
| Placement | Non-Removable | |
| Battery capacity | | 4230 mAh, Non-removable Li-Ion |
| Other | Vivo Y66i | Oppo A3s |
| Release date | | 2018, July |
| Sensors | Accelerometer, Proximity, Light, Gyroscope Sensor | Accelerometer, proximity, compass |
