Hello, I am new to photography and want to choose an entry-level model. I am hesitating between Sony a550 and Nikon d3100 d5000. Please give me some advice.

Image quality...

This kind of low-level reason is too much. It is known to the world that Nikon uses the CCD and COMS provided by Sony.

In terms of machines, Sony α550 is better than Nikon D3100 and D5000

1 For Nikon system machines, the higher the end, the more reliable they are. When choosing Nikon, at least start with D90, because there is no body below D90 Motors, and many Nikon lenses do not have motors of their own, which means that you will not be able to use many classic lenses in the future, and you will have to spend more money to buy lenses that include focus motors.

2 If you plan to buy a mid-range machine such as D90 or D7000, then Nikon is good, but if you are entry-level, Sony's entry-level machine is still quite good. Recommended Sony α580. Paired with a 16-105 or 16-80za Zeiss lens, it should be enough for the first two years of entry, and the body performance is also good.

3 As for the image quality, there is no standard. Some people think that Canon is not sharp enough, some say that Nikon's image quality is yellowish, and some say that Sony is not good and that is not good. But when really choosing a machine, you have to put aside the interference of the brand. Even in a market as big as Canon, the reflector is removed. It doesn’t matter who has the most market, or whose product is better. Go to the store to touch and take a look, and ask someone familiar with it. At least, I have used Nikon and Sony, and my feeling is that each has its own merits, it’s up to you to take what you want. I like the color of the picture, and I think the combination of Sony + Zeiss is good.