I use the main full sized on one screen and small windows for the slaves on the second screen. My browser takes up more room on my secondary monitor than my slaves do. There's really nothing I need to see in huge, spectacular detail on the slave screens that I can't see on my master screen.

If I ever do need a slave screen bigger for some reason, I have the option to swap it to full size on either monitor. I've found increasing the screen size for the slaves does absolutely nothing for my situational awareness and actually becomes rather distracting.