As Aluminium does not degrade over time, the windows will not have any alignment issue longer-term. This will ensure that the window is weathertight, soundproof and dust resistant as noise, dust and water travel through small gaps between the glass, hardware, sash and frame. Hence, the fit between these parts is essential in keeping the window soundproof, weathertight and dust resistant.
Therefore, a soundproof window that is made of aluminium will have the same soundproofing quality even after 10 or 20 years. In contrast, uPVC windows degrade over time and is its soundproofing quality last probably half as long as aluminium windows. In addition, due to the thickness of the glass used for soundproof windows, a normal window sash could weigh up to 120kg. This weight will speed up the degrading of the window frame causing windows to sag, which is a common problem with uPVC, going by the thousands of case studies online.
Example of sagging uPVC windows: