If you are considering the 18-70mm, you may want to confirm that it has a weather-sealed mount, and see if your other contenders are similarly sealed, as the D7000 has some level of weather-sealing. (My wife has an 18-70mm, and I think it has a gasketed mount.) I do not think, however, she has used the 18-70mm on her D7000, so I cannot comment on how it performs on a 16 MP camera. It seems to do well enough on a 6 MP D70s.
Canon 7D/5D/40D/1D2N; Nikon F6, FM3A, & Coolpix A; Canon 40mm Pancake, 135L, 50L, 35L, pre-II 50mm 1.8, 100mm 2.8L Macro, 10-22mm EF-S, 28-135 EF, 400mm 5.6L; Nikkor 50mm 1.2 AI-S, 50mm 1.4G, 50mm 1.8D, 16mm 2.8D Fisheye, 180mm 2.8D, 100-300mm 5.6 AI-S; Tokina 17mm & 100mm 2.8 Macro