Want to start with Nikon's SLR camera, what do you recommend? I hope to comprehensively consider the preservation and cost performance, thank you!

Digital cameras, like computers, are updated quickly and are bought for use. As for preserving value, forget it! You're not going to sell it anyway, so, to be honest, these cameras you quoted are not worth the money!

Since you like clear and soft things, I think as far as definition is concerned, it's ok! If the price is not considered, the first choice is D7000, which is a new model listed this year and belongs to the mid-range model in Nikon series. Very well controlled. Powerful and advanced function, exquisite picture quality and high definition, powerful continuous shooting function, fast and accurate focusing! Much better than D5 100, D3200 and D90! D5 100 and D3200 are also acceptable, which can meet your needs. However, compared with D7000, there is still a big gap in operating feel, image quality and function. D90 is not recommended. It was made in 2008. It's too old. Let's get rid of it!

I hope my answer can help you and wish you success!