1. Cost of living: The cost of living in Xiamen and Macau is quite different. The average house prices and prices in Macao are much higher than those in Xiamen, but the wages in Macao are relatively high. If your brother has a high cost of living, you can consider going to Macau.

2. Job opportunities: The job opportunities in Xiamen and Macau are very different. Macao is a city mainly engaged in service industry and tourism, but there are also some electronic and chemical industries. Xiamen, on the other hand, is a manufacturing-oriented city, with export trade as the mainstay. If your brother wants to engage in service industry or tourism, you can consider going to Macau. If he wants to engage in manufacturing, he can consider going to Xiamen.

3. Educational resources: Xiamen and Macao have different educational resources. The quality of education in Macao is relatively high, but the university ranking is not as good as some universities in Xiamen. If your brother wants to get better educational resources, he can consider going to Xiamen.

4. Cultural background: Xiamen and Macao have their own cultural backgrounds. Xiamen is a part of Fujian and has a long history of overseas Chinese culture, while Macao also has its own unique Portuguese culture. These factors may affect your brother's life and career development.

To sum up, whether to choose Xiamen or Macau depends on your brother's personal situation and career planning. If he has a high cost of living, or wants to engage in service industry and tourism, he can consider going to Macau. If he wants to engage in manufacturing or get better educational resources, he can consider going to Xiamen.