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The D300 is a much faster camera. Faster burst rate, bigger buffer, faster/better AF performance in both initial acquisition and tracking, better handling, more physical controls, less menu diving. It's also a more rugged camera.
The D7000 has much better high-ISO noise performance, and 4MP more. But AF is slower, burst rate is slower, handling is slower.
If you can afford to take your time with every shot and plan/setup comfortably, then I'd vote for the higher IQ of the D7000. But if you need to move fast and shoot fast, or you're interacting with people who are doing stuff, then I'd prefer to have the lower (but still sufficient) IQ of the D300 and fewer missed shots.