Should buy Nikon or Sony dslr camera?

Should I buy Nikon D5100 or Sony alpha 37?
(Reason & Pros and cons of both the cam)

Sony dslr

Whichever one you like… It makes no difference in the results. Nikon accessories are easier to find if you shop in a brick and mortar store. If you shop on line, then it doesn't matter.

They both take photos, and you can't tell which camera created which photo just by looking at it. That also applies to similar bodies from Canon, Pentax, Oly, Samsung, Panasonic… They all do the same thing the same way.

Shoot mostly pictures? DSLR.
Shoot a good mix of photos and videos? SLT.
Shoot video a lot? Digital camcorder.

I'd buy Pentax over either, and many would tell you to go Canon - apart from the Sony's better video, it doesn't matter.

Find a dealer, handle them and buy the one you like.

There's no comparison between the both, if you want to compare, compare between Nikon products and Canon. Sony is relatively new in the DSLR market.
I personally purchase Nikon 5100 and I'm really happy with it. Nikon camera's are more tougher then Sony ones and they have more variety of lenses. Third party Lens makers have more lenses for Nikon and Canon then Sony.
Check the link of Nikon 5100 pics..

Sony purchased Minolta and the knowledge that Minolta had within Photography is quite impressive (they exchanged technical knowledge of electronics for optical knowledge on lenses with Leica),

The build quality between these two cameras isn't worth comparing, there's not a lot in it.

Nikon professional cameras have an improved build quality over their 'enthusiast' cameras. Both the alpha 37 and D5100 are aimed at entry-enthusiast level.

All Minolta AF Lenses are compatible with the Sony Alpha 37 and the independent brands offer a comprehensive range of lenses for Sony/Minolta fit.

I bought the D5100 last week and its a decent camera, my sister uses the alpha 37 and loves it, both will give you great results, try and get your hands on both of them in a specialist store and take your pick of the one that feels best in your hands. It always works for me!