LAX - lounges in TBIT are terrible. I believe they are being redesigned but my experience of a terminal transfer and the old/worn lounge made LAX a NO for next time.

YVR - nice but I got lost during the transfer in customs - I went to what I thought was the line for those transferring and not entering the country. Long story short, I was stuck in customs for a while until they cleared me to go where I needed to go.

SFO - new terminal and nice dedicated lounge. Yes, there is the weather risk and a terminal transfer.

Hopefully you get the redesigned BA FC experience! Good luck!