The aluminium can take incredible amount of abuse and damage and still can be repaired, whereas a broken sheet of PC is just a broken sheet of PC, even if it's formed as a luggage

Having said that, the young ones' PC luggage have held up for over a decade now.
As for the colours - the coloured aluminium ones I saw were "sand blown" types, so I don't think those can even peel off, but with any scratches, damages the original (natural) aluminum colour will shine through.