Two plain T-shirts can look similar in a photograph yet have different prices. The logo or fabric weight alone will not explain that difference. Focus on what you can actually compare.
The smaller size sits well at your shoulders. The larger feels better around your waist. That does not immediately make either one wrong. Separate the different parts of the fit before deciding.
Do not start with ten colours. Take out the trousers you wear most often. They make it easier to see which shirt adds something and which one mainly appeals in a photograph.
The same tee looks different when you show the waistband. Tucking it in changes the proportions. Leaving it out may feel more relaxed. Start with your trousers, then check the shirt length.
White can look different in a product photograph and in your own mirror. Lighting, fabric and tension all matter. Do not decide from the colour or fabric weight alone.