It all depends on how well you want to protect your gun and how much you want to hide what you have. I want my weapon protected as much as possible from impacts, and I live outside a city in a gunfriendly state (even if my neighbors saw me loading long black cases with "BUSHMASTER" in big letters on the side, they 'd be more likely to ask if I wanted to go shooting with them than anything else) so concealing the fact that I have rifles is no concern at all to me.
Since I want protection and couldn't care less about "discreetness", I just use the hard case that came with my rifle. If I lived in LA, I probably would do something that doesn't scream GUN. A guitar case, maybe?