400 is a good price for the D3100, but they don’t seel for over as grand, IIRC their around ~650 new for a kit with an 18-55 kit lens
This, most brand lenses Nikkor/Cannon are all good optically. They will take nice sharp clean images, but they only get better the more you spend and depending on how fast the lens is.
If Dave (love4boosts) d3100 coems with the 18-55 kit lens it would be a good deal, its actually a nice camera, just not as feature heavy as say the D5100 and up, but will take any Nikon AF-S lens (pretty much any new lens)
If anything, i’d pick up any cannon/nikon with a kit lens, and a 35mm or 50mm 1.8 lens for low light and general shooting conditions. To be honest a lot of shots can be done with a 35/50mm lens unless the condition/location doesnt allow for it, just move closer or further away.
Depending on the kit lens that comes with the camera, I know nikon does 18-55 for some or 18-105, you may want to get a zoom lens as well
As far as Nikon vs Cannon, its personal prefrence, I like Nikon… I always have, i’ve used friends cannons and I just prefer the Nikon layout and displays.
Id get either brand in the price range you want, and depending on the kit lens id get a 35mm 1.8 lens and a ~50-200/70-300 lens if the kit lens doesn’t have a long focal length
I love my wifes Nikon D5100, it really does take some great photos, and the 18-55 kit lens that comes with it takes some really sharp pictures, just sucks in low light, only reason I got a D90 is because she was sick of me using it all the time and it was a bit small for my big hands, plus I like a heavier camera, but its got a great image sensor and is really easy to use and the button layout is very nice compred to even my D90. IIRC its $749 right now at best buy for the kit with the 18-55