Both window materials have their advantages and disadvantages so it really comes down what you can live with or without in terms of quality and construction.
The pros of aluminum are: it is lightweight, it’s cheap, and environmentally friendly. The cons are they tend to attract heat and require maintenance. The pros of UPVC windows and doors are: easy to clean and maintain, heat resistant, reduce noise, and they are dust proof.
The only con about I have found is they tend to be weaker compared to other frames, however, as far as I know, they have never caused a problem with walls or buildings coming down.