La Palma has 2200m of runway while La Gomera has just 1500m - this makes routes to La Palma with a 150+ seat jet from northern Europe much more economically viable
La Gomera really is a lovely place - and I'd happily go there tomorrow. I just think that if IAG were going to open a new route from La Gomera outside the Canary Islands, somewhere like Madrid is going to be much higher up in the priority list