Definitely get the one you like the feel of.
Take a look at lenses too. Spend more money on lenses, you'll see far more of a difference from quality lenses than from spending more money on a better body.
For landscapes, the nikkor 18-55 VR kitlens is supposed to be very decent, I expect you can get a D3100 bundled with one of these.
For something a bit better for landscapes, a tokina 11-16mm will go a lot wider than the kitlens to really take in huge landscapes, or something like a tamron 17-50mm (non VC version is sharper) f/2.8 for a similar focal length range to the kitlens.
A tripod is a must for landscapes, you can do much longer exposures and get sharp shots on a tripod, so you can shoot at ISO 100 in any light and no worries about camera shake.
For close up (I presume you mean getting close to small subjects) a good macro lens is best, something like the tamron 90mm f/2.8 or sigma 105mm or 70mm will perform nicely for not too much cash. You'll need flash, a tripod or good light for macro though.
For sport, something like the nikkor 55-200mm should do OK on a budget. It won't be great in low light, but you're looking at spending a LOT for something faster like a 70-200 f/2.8 though.
Hope that helps.