Which is better uPVC windows or aluminium windows?

uPVC windows against aluminium windows won’t be a fair fight at all, because uPVC would win by a long shot. The simple physical nature of aluminium to be an excellent conductor of heat cause your rooms to get hotter in summer & colder in winter & thus shooting your energy bills to extreme heights. Whereas uPVC is an excellent insulator & even offers you a bonus feature of UV radiation protection so I would say it’s a no-brainer that uPVC is a clear winner.