Having 70-200 f/2.8 VR, you are already holding one the best trinity lens in Nikon series, adding a TC 1.4, gives you up to 280mm which is pretty near 300mm or if you want, go get a TC 1.7 which gives you 340mm. Using teleconverters gives you slower effective lens, basically is "multiplier * original aperture f/stop" For TC 1.4, your f/2.8 lens becomes f(2.8 * 1.4), For TC 1.7: f(2.8 * 1.7) and TC 2 f(5.6). Forget the 70-300mm, you are wasting money because your are repeating your focal length for 70-200mm range. Since you already own a 70-200mm, means weight is not an issue for you right from the beginning, if you feel it is any issue, then sell it away and gt the 70-300, but there you go, you wasted $ and also you get a much slower lens from 4.5~5.6 which wonders why you got the 70-200 in the first place
Both TC 1.4 and TC 1.7 gives good enough sharpness when use with 70-200, only TC 2 will give you a less than impressive image quality. At TC 1.7, your lens is still faster than 70-300mm.