Among Nikon D3100 and D3200 which is best and why please suggest me?

Among Nikon D3100 and D3200 which is best and why please suggest me?

Nikon D3300 because it's the newest and has the latest features.

Striking images, even in low light, via a remarkably compact body…

… Despite the D3300's extremely compact body, it features 24.2 effective megapixels and the new EXPEED 4 image-processing engine. With NIKKOR interchangeable lenses, the camera delivers razor-sharp detail even in low-light situations, while a range of advanced technologies makes it incredibly easy to use, even for beginners.

Between the D3100 and the D3200, the latter is better for the simple reason that it's newer. If your criteria is cost however, the better one is the D3100 because it's cheaper.

Why only Nikon?

While the D3200 has higher resolution, and the D3100 is cheaper, there are alternatives.

The Canon Rebels autofocus with any lens made to fit them.

The Sony SLT A-58 uses the same sensor as the D3300 (made by Sony in the first place), has body-mounted anti-shake, better video performance, and - again - autofocuses with any lens made for it (all Sony SLTs have body motors).

The Pentax K-500 has a pentaprism viewfinder with 100% coverage (better than either Canon or Nikon - the Sony uses a 100% electronic viewfinder) uses the D3300 sensor, has body-mounted anti-shake, and takes not only any autofocus lens made for it, but allows metering with manual-focus lenses (these Nikons take MF lenses, but won't meter with them).