Here is a list of five best phones that would come under your budget of Rs.25000
1. OnePlus 2
Framed within a premium stainless steel body the phone is beautifully designed with a multi-touch IPS 5.5 inches screen protected by a Corning Gorilla Glass. It has a 3 IPS LCD full HD display of 1080 x 1920 pixels and 401 PPI, with 1500:1 contrast ratio; and you get a 178 degrees viewing angle.
Based on Android Lollipop 5.1.1 with Qualcomm Snapdragon 810 (64 bit with 1.8GHz Octa-core SoC) Processor, the phone runs on OxygenOS with 4G LTE connectivity, an Adreno 430 GPU for its graphics.
The device carries a 4GB LPDDR4 RAM with 64GB eMMC5 storage. This future ready phone comes with long lasting 3,300 mAh Li-Po battery, slots for Dual Nano SIMs, USB Type-C port, Fingerprint sensor and 3-way physical alert toggle switch.
There is a best-in class primary camera of 13MP with f/2.0 Aperture of 1.3 µm Pixels, accompanied by 6-lenses, Dual LED Flash, and an advanced Laser Autofocus feature with Optical Image Stabilisation (OIS). The front facing camera is of 5MP.
2. HTC One X9
Powered by octa-core MediaTek Helio X10 processor, the HTC One X9 is a 5.50-inch phone with touchscreen display and a resolution of 1080 pixels by 1920 pixels at a PPI of 401 pixels per inch. The display is protected by a Full HD 1080p Curve edge Gorilla Glass.
Running on Android OS, v6.0 (Marshmallow) with 3GB of RAM, the phone is packed with a 32GB of internal storage which can be expanded up to 2000GB through a microSD card.
The HTC One X9 comes with a 13-megapixel primary camera and a 5-megapixel front shooter for selfies on its rear. The cameras are equipped with features like dual tone LED flash, Optical Image Stabilisation (OIS), Pro mode with manual control and RAW format, HDR mode, Full HD 1080p video recording Live make-up, Auto selfie, Voice Selfie, Selfie timer up to 10 seconds and more.
This Dual SIM phone has Nano slots for both the SIMs with 3G UMTS, 4G LTE
Battery Capacity of this phone is 3000 mAh
3. Moto Z Play with Style Mod
Running on Android 6.0.1 Marshmallow, this phone is powered by a 2 GHz Octa-Core Qualcomm Snapdragon 625 processor with a 650 MHz Adreno 506 GPU for its graphics. The storage includes 3GB of LPDDR3 RAM, with 32GB internal memory that can be expanded up to 2TB.
The device comes with a dual micro-SIM dual-standby (4G+4G), 4G VoLTE.
It is a phone with a 5.5-inch super AMOLED 1080p full HD Display with 403 ppi. Other features include finger print reader and water repellent nano-coating.
The 3510 mAh battery with TurboPower charging runs the phone all day long with 8 hours of power in 15 min of charging.
For photo and video shoots, it carries a 16 MP dual autofocus camera that has features like laser focus and PDAF, color balancing dual LED flash, 4K video recording (30 fps). For selfies it comes with the standard 5 MP front camera along with display flash.
The best feature of this phone is that you can transform it magnetically by clicking on the Moto Mods onto your phone. You can convert it into a movie projector, a battery powerhouse, boombox, and more. But you need to purchase the Mods separately.
4.Lenovo Vibe Shot
The Lenovo Vibe Shot runs on Android OS, v5.0.2 (Lollipop) based on a Qualcomm MSM8939 Snapdragon 615 Chipset and an Octa-core (4x1.7 GHz Cortex-A53 & 4x1.0 GHz Cortex-A53)
processor. For graphics it has inserted a Adreno 4051.7GHz 64-bit octa core processor.The storage includes a 32GB Memory with an expandable 128GB memory.
The 5.0 inches Display is of IPS LCD capacitive touchscreen with 16M colors and a 69.3% screen-to-body ratio with a Resolution of 1080 x 1920 pixels and Multitouch functionality. All this is protected by a 3.0 Gorilla glass.
The camera has 16MP in the Rear and 8MP in the front. The features in them are Manual shutter button, Pro and auto shooting modes, Optical Image stabilization and a Low light sensor.
5. Sony Xperia M4 Aqua Dual
This smartphone model from Sony runs with Android v5 Lollipop operating system powered by a 1.5GHz+1GHz 64-bit Qualcomm Snapdragon 615 octa core processor. For graphics it has an Adreno 405 GPU,
The storage of the device has in it a 2GB RAM, with 16GB internal memory which can be expanded up to 128GB.
The phone has the standard 5-inch HD capacitive touchscreen display with 1280 x 720 pixels of resolution.
This is a dual SIM (GSM+GSM) phone carrrying a 2400mAH lithium-ion battery that gives a talk-time of 13 hours 17 minutes along with a standby time of 493 hours.
For photography the phone is packed with a 13MP primary camera and 5MP front facing camera with features like auto focus, image stabiliser and more.
For the choice of an Operating system, even I would go with the other experts and suggest you to stay with Android for a number of reasons.
1. Ease of use.
2. Easy upgrade
3. You will have more number of phone models to choose from.
4. Available at both low to high prices.
5. More number of apps available for it.