I choose SAS for basically all my LHR-ARN trips because on the dates when I wanted to travel, SK had reasonable fares (as low as £50 and I think I've never paid over £100) whereas BA was always asking for way more than £100.

My SK flights have always been 80-100% full too - though sometimes this is because SK combines two flights into one.

This means the only time I fly BA on this route is using Avios, but at 6500 / 7500 avios + fee, it doesn't make sense to do so unless SAS is charging £90+

I use Norwegian when I want to fly from LGW