The gold sub isn't about sales though, it was argues as big about the quality of the service.|
As Edge mag rightly point out, Sony will have a harder time waving away the PSN downtimes no multiplayer is pay only on PS4.
Also you do get general (no Gold required) sales on XBL these days, and have for so for a couple of years. You just get more with Gold.
Don't get me wrong, PSN is great value with the IGC etc, and Sony's sale philosophy is better/clearer, but just making the point that (unarguably) XBL is the more stable and reliable service.
Why look, it's a blog: