These four machines cannot be compared together because they have different grades. 50D and 40D are mid-range Canon digital SLR cameras. 50D is an upgraded product of 40D. All indicators and performance are better than 40D. The price of 50D is also much higher than 40D. 450D is the entry-level among Canon digital SLR cameras. All indicators and performance are good, and the price-performance ratio is relatively high. 1000D can be regarded as a simplified version of 400D or 450D. The performance indicators are not as good as 450D, but the price is much lower than 450D. In terms of good performance, the 50D is certainly the best among the four, but it is also the most expensive. The body is about 7,000 yuan. In terms of practicality, I feel that the 450D is just fine. It has good performance and is moderately priced. The body is about 4,000 yuan. You can decide based on your own purposes and financial budget.