Im GO and I agree above- the benefits show up when flying other OW partners.

1. When flying BA long haul J, BA allows me pre-select seats after booking, free of charge.
This is really helpful because BA has probably the worst seat map- 8 J seats per row!
This offer saves me about 200 Euros for return ticket.

2. When flying AY, IB, AB intra Europe Y, I would not only use the lounges, but also get one luggage free of charge. I'm happy worth these.

Comparing to SL, well, I got greeting onboard almost every time when flying CX/KA Y and Y+. However, I don't see it a big deal or " benefit"