A straight comparison of sightlines, thermal behaviour, span capability and cost.
Both materials make excellent modern windows. The right choice depends on the size of the openings, the look you want and how much of the budget belongs to the frames rather than the glass.
Here is the comparison without the sales gloss.
Aluminium is stronger, so frames can be slimmer for the same opening. On large windows that means noticeably more glass and a more contemporary look. On small openings the difference is barely visible.
uPVC is naturally a poor conductor, so it performs well thermally at a lower cost. Modern aluminium uses a thermal break to close most of that gap, but it is engineering rather than material that gets it there — which is part of why it costs more.
Powder-coated aluminium holds colour extremely well and suits bold or dark finishes. uPVC foils have improved enormously and give convincing woodgrain finishes at lower cost. Both need little more than cleaning and occasional hardware lubrication.
Large picture windows, wide bays and contemporary extensions usually justify aluminium. Standard residential replacement across a whole house is usually better value in uPVC, with the savings put into better glass.
We quote both materials against the same openings so you can see the real difference in price and sightlines.
Untreated aluminium conducts heat readily, which is why quality systems use a thermal break. A thermally broken aluminium window performs well; a cheap non-broken one does not.
Yes, and it is common — aluminium on a large rear elevation or extension, uPVC elsewhere.
Both are long-life products when well installed. Aluminium is more rigid across wide spans; uPVC is more forgiving on cost.