I mean even a piggyback isn't fool proof, the jb4's, bootmod, etc etc are nice but all they are doing is fooling the ecu, if something breaks and bmw does a dive in there they are going to notice it, at least with the full tune you can make it as conservative or extreme as you want. Personally speaking tuning and piggybacks are a real cautious area for me on these German cars.
They deserve to be tuned but then you gotta check what else gets more wear and tear, it's worth it but exhausting knowing all the possibilities