&quot;<i>Gatwick Express goes non-stop to Victoria Station, while Southern does have stops</i>&quot; That's true, but Southern still only takes 5 minutes longer to Victoria than the Express. It's not as though one has change trains or anything

If one is not careful, one might indeed have to change trains. For example, the Southern 10:37 changes trains at Clapham Junction. The overall trip still only takes 38 minutes, though. Other carriers change at East Croydon.