Which of the two dslr camera to buy?

I'm looking a Dslr camera.to shoot some video stuff… Only video basically… But confused between Nikon d5200 and Sony alpha a58m. So please help which one would be better for videos. Some people say camcorder but don't wana buy a camcorder. So please suggest.

They are both have the same video functionality, so your videos will be about the same with either camera. I would encourage you to look at either the Pentax K50 or K5II instead. The reason is the Pentax bodies use Motion JPEG for video which is superior to the MPEG 4 technology found in the Sony and Nikon cameras. Additionally, the Pentax (like the Sony) has built in image stabilization which mean you get IS will all of your lenses instead of specific models from Nikon. The Pentax is also weather and dust proof unlike the Sony and Nikon. The video format, IS, and weather/dust proof make the Pentax a superior choice. The Sony, however, has a tilt screen which may come in handy depending on how you shoot, but the Pentax could be hooked up to a small monitor if needed.
I would take a look at the lens lineup between the Sony and Pentax and see if either one makes any specific lenses that you need/want that the other doesn't. It's a toss-up between the Sony and Pentax.

The Sony will blow the Nikon (or any other DSLR) out of the water for video performance, because it isn't a true DSLR, but a hybrid unique to Sony called an SLT (fixed mirror/electronic viewfinder).

To be fair, even the Sony is a poor substitute for a camcorder.

Why do you want to buy a "stills" camera for videos?
You should be looking to buy a Video Camera or Camcorder. Far more versatile for what you want.

The alpha is better but at around half the price, a Sony Handycam would allow you to shoot much longer and autofocus much better.

Camcorders are the right tools for capturing video. If you don't know why exactly you want a dSLR for video, those people are precisely correct.

Your decision of not buying a camcorder is right. Sony's DSLR camera are very popular for their video recording quality. Their exposure, color scheme and focus is really good when it comes to recording video. Go for Sony.