how would you rate each then:
atari(with big blues)
Usually, if the Big Blue and rectifier are good, these are just fine. Besides, the true voltage for the Atair pcb's is usually from the Audio Regulator Board. If you have one that's working or can be fixed, it's always best to use it since it outputs voltage that the switchers cannot. Still, if I have issues with the AR boards, I'll sometimes install a switcher just for the +5 line.
Are there any? Maybe the System 1 and newer cabs? A lot of those were built with some type of switcher in them, so replacing them if they are bad is no problem.
Depends on the game. Pac-Man and Ms. Pac-Man power supplies output AC which is converted to DC by the game pcb. Galaga and others used a different type of power supply board. I've used switchers in both - usually in the Pac style if the transformer is bad, and in the Galaga types if the PS doesn't want to be fixed.
I have no problem with MCR's when they're properly rebuilt, but the battery on the PS sometimes leaks so much corrosion that it's easier (and quicker) to just get an MCR adapter and use a switcher instead.
williams(joust, def, robo, etc)
While there are switcher kits for these, too, I prefer to rebuild the originals if they break down. They are VERY reliable when rebuilt properly.
Most other games have some type of switching power supply in them already, so putting a new one in is fine. I don't go replacing working power supplies in my games, though. If they have a problem that I can't fix, or can't replace due to lack of parts, then I'll go with a switcher....