Its not coding vs an installer. Doesn't matter if you have the best installer in the world and for argument sake can be in a BMW factory and install it like it was suppose to be in the car when it was first built. still got to take the time to wait for it to get done. which would be hours vs a couple minute's if not less.
Coding can accomplish retrofits and change vehicle order (VO)
Pros vs Cons. My opinion will always be coding. Something major is time and money. Cheaper and faster to get it done for coding. Sure you might get something a little bit extra by installing a module but not enough to make me sway my decision.
Example: Sure with the one touch remote for window open/close you have to hold the remote button down through the entire cycle vs with a module you may not have too. But the cost of the module would be more, the time for install would be longer and they would have to open up your can interior and wire it. Personal I don't want any of the internals touched as much as possible and I'm sure many would feel the same if given the choice.
But its all opinionated. Everyone will have there own opinion on this topic. I'm just going to show what coding can accomplish in this post and I'll let the individual decide.