These days the varieties or options for smartphones available in market is more than actually required. Too many options, same looking configurations and big price differences.
The basic thing that we check while buying a smartphone now days are
1. Processing Speed
3. Storage Space
4. App Installation Space
5. Display Camera, Battery, Dual Sim Option and All those ;)
The processors vary from device to device. I Will categorize as following.
Mediatek or Qualcomm
These two are the Smartphone Processor giants with Intel still struggling. I compare Mediatek and Qualcomm like AMD and Intel. Both have their own market. But what I suggest is that Go for Qualcomm devices if you are interested with custom development over your phone from XDA Developers, else Mediatek is doing well.
Number of Cores
These days we have upto 8 Core CPUs, but very few of us know that only 4 cores run parallel in almost all devices. Actually most devices are 4+4 Core devices, 4 are performance cores and 4 are power saving mode cores. So this is not the No. of cores that matters the most, it is the Clock-rate per core and the CPU architecture that matters the most. Latest architecture @ 1.5 GH will surely perform better than an older architecture with 2 GH or higher clock-rate
More is the RAM, more multi-tasking is possible. But wait, is just a BIG RAM with a good processor sufficient to give you good performance? Answer is clearly NO. The closest word to RAM n Androids is RAM Management. Yes. Its the RAM management that matters a lot. Check a Xiaomi or Samsung device's free RAM at any time. Out of 2 GB, you will hardly find 300-400 MB Available RAM, on the other hand, most Sony or HTC devices have generally 700-900 MB free available RAM at ideal times. This is what matters. So choose wisely.
3. Storage Space
Storage space is a basic need. Most phones come with expandable storage options, those who do not provide storage expansion option, avoid them. Out of several other reasons, the option to save your data in case of phone crashes and also the hunger or more space is never ending for humans, expandable storage is a must.
5. App Installation Space
App storage apace or App Installation Space should not be confused with media storage space. Consider an mobile advertising 8 GB internal storage. Mostly out of this, you get a max of 5 GB for your personal use. Our of this, only a small space is provided for Application installation. Although there are options to move data to SD card, but this can never compensate the internal storage space.
6. Display Camera, Battery, Dual Sim Option and others
I will close some points really fast.
Too high resolution means better picture quality but also a big difference in batter consumption. And bigger displays have more chances fo getting broken during accidental falls. This is a simple science and applies to Gorilla glasses also, 3,4,5 whatever it is :P.
All of us know that megapixels are not everything. So please try to get hands on test before selecting a phone if you take camera quality seriously. And yes, If you are selecting a Sony mid rane device, take extra precautions, Sony Xperia M, Sony Xperia C and Sony Xperia M 2 are some of the most horrifying examples.
Dual SIM Options
Its totally upto you. Well if you get a Dual SIM phone, and use single SIM, then you have afree SIM slot for your new Girl Friend. Its separate for each.