In my opinion, the Beacon of the Reed Sea gives a better bang for the buck. You need to spend money to get the Serpent Spine via the battlepass, whereas you can wish on the Beacon of the Reed Sea's banner if you have enough fates saved already. I haven't seen any change in the battlepass weapons and don't expect Hoyoverse to change them in the future. It's better to stick with the ongoing meta than go for the weapons that can be purchased whenever you want to.