First, you want know about mobile mother board .
Mediatek is always cheap and high performance, but it's value is less then Snapdragon.
TATA not equal to Audi ,if both have same feature
Snapdragon is premium quality and have high reliability. Today market have fight between Snapdragon with MT. But SD board always win , you can see that REDMI 1S, MOTO G and many...
You asked "which one best SD615 or MT 6572 ?"
The Qualcomm® Snapdragon⢠615 processor sets the standard for high-tier
mobile device design with the industry's first octa-core **64-bit capable
CPU architecture**, featuring integrated advanced 4G LTE for the optimal
balance of performance and power, along with an RF Front End solution,
for virtually seamless communications and outstanding battery life.
MediaTek MT6572 brings dual-core performance to entry-level smartphones
without taking a toll on battery life. Based on the energy-efficient
dual-core ARM- Cortex -A7 processor, MT6572 features a cost-optimised
system level design that simplifies product development, **reduces
manufacturing costs and speeds up the time to market**
My opinion Snapdragon is best . value for money and can resale .
Plz keep in mind - Apple mobile achieved gold opportunity in the world by created 64 bits architecture and 64 bit OS .
Snapdragon 415,615,815 < above,they are have 64 bit CPU architecture , and Android lollipop OS only have 64 bit option . before you buy check all information.and above 3Gb RAM is added advantage . it's will make like as computer performance.
regards
r.parthiban 