I can only recommend the SAS Plus product when it comes to intercontinental flights. For the short leg to Stockholm you should not expect an empty middle seat when the flight is almost fully booked. I very much like Sas new cabin design and also the service is appropriate, but Nordic style ( meaning you need to speak up if you want something).
If you credit to miles and bonus you will also receive 200% of the miles for all Plus booking classes ( A, B, P, S and Y ) while discounted Lufthansa PE will only give you 100%.
I am eurobonus member so naturally I prefer SAS and I have been upgraded quite often on my last flights being a premium frequent flyer. I cannot give any comments regarding *G upgrades. They will prefer Eurobonus status members first and the plus cabin on Hong Kong flights has many more seats compared to business class. So I would not expect it.