Advanced Brain Monitoring (ABM):  http://www.advancedbrainmonitoring.com/

You can find a comparison between devices here (https://en.wikipedia.org/wiki/Comparison_of_consumer_brain%E2%80%93computer_interfaces) it is not complete though. I have worked with many devices, among those I would say g.tech was better in some senses: http://www.gtec.at/

http://www.gtec.at/

https://en.wikipedia.org/wiki/Comparison_of_consumer_brain%E2%80%93computer_interfaces

See

https://repositorio.ufsc.br/bitstream/handle/123456789/90454/192952.pdf?sequence=1

or

http://repositorio.ufsc.br/xmlui/handle/123456789/82114

 Manoj,

The Best device will depend on the scope of your research, and which components of the brain signal you are hoping to analyze.  If you could share a bit more on what you are hoping to achieve it should ensure that you will purchase the best device for you.  I am a bit biased to the ABM products, but depending on your needs we may not be the best device for you.