its pretty simple if you want upgrades go with united. United is the most generous airline in the world regarding upgrades. GS can upgrade any fare including award tickets (besides BE) the average GS will accrue around 500 plus points enough for 17 upgrades to Polaris from premium economy per year. Domesticly upgrades are free and are very easy for GS unless your flying peak sfo hours. Global services also comes with united club access on every flight. Most GS have MM status which allows you to share your GS to someone else. BA has the upper hand with lounge access however especially if you have a CCR card. However GS has private checkin facility's just for GS that send you to the front of security. GS also have some special exceptions regarding award and upgrades which I won't get in to. However their upgrades clear far better than a 1k. I personally think GS is better than GGL especially if your a million miler.