What sort of shots are you going to take in low light?
Though having had both cameras I can say the low light performance is pretty similar. Though for non flash low light I use a tripod and a remote release. For both cameras I only rarely went above 400, and then only to 800 if I had to. When shooting in low light with both cameras I would recommend exposing to the right (brighter if possible) without blowing highlights. Or in my case I have a couple of YN-506 flash guns, stands, snoots, etc brolly's and remote triggers. Cheap via ebay, and some stuff like the snoots home made.
If you want to crop or print large go for the D3200, I did and love the picture you can take.
Here is a recent picture taken with my D3200, a 55-300 Nikon lens and in woodland so light was interesting, bright areas with lots of shadows:
if you could see what i have seen with your eyes | Flickr - Photo Sharing!
I am not on my home system so I couldn't upload a version.
I tend to print out pictures as large as possible on A4 for the majority, but also do numerous prints on A3 paper and the picture are great, even with cropping.
I also found using the higher resolution and thus less forgiving sensor has helped me improve my technique, though I still have a lot of further to go, but I am enjoying learning and occasionally getting a good shot.
More details of what you want to photograph would help. In my case I am biased, I love the D3200 and my next upgrade will be to the similar pixel count D600 (though I dream of a D800, but need to nail the technicalities of good cameramanship first.)