Been just thinking about that. Basicaly in IV you have the most freedom in choosing how you want to complete a mission. And I also prefer the most cleanest and most professional ways, like killing Clarence Little with one sniper shot from that crane nearby, or shutting up Tom Goldberg silently with a knife. Or in Snow Storm you can actually sneak around the whole building leaving most of the gang members alive just stealing the coke which is even helpful because when the Noose arrives they start to fight with each other leaving you with a clean(er) getaway. And this just fits Niko's character so much better than going Rambo all the time.
There's also the aftermath of the funeral when you jump into the Romero you should park in an alley and the guys in the car arrive to chase so just jump out and shoot them. Makes the drive to the graveyard more peaceful.
Also Late Checkout is more fun if you have a helicopter and is more professional way of completing it.
I like completing missions with the least amount of disturbance to others and no police.