I only fly for leisure so not nearly as often as people on here. I have flown with AC signature and UA Polaris and personally I’d rate AC slightly better but they’re pretty comparable. I’m 6’2 and found the AC seat roomier (though the table placement was irritating). I’d give food a slight edge on AC (again this would be personal preference) and at YVR you’ll have access to the signature lounge, assuming you’re paid J. I’ve only used it in YYZ. I preferred it to the Polaris lounge dining wise, but it’s more a restaurant than a lounge and the Polaris lounge is way better than the Maple Leaf lounge. Crew wise, I generally find AC better than UA on average, but at its very best UA was better than AC. But that’s really luck of the draw with the crew. Im sure others will disagree but that’s my personal little review! Good luck!!