The red dot has really come into its own in the last several years. I've got a bunch of SIG red dots, over a dozen at last count. Every flavor including the big Romeo7, several 4's and the little reflexes. The Romeo5 is ridiculous for what it costs. If I'd bought it first, I'd probably have a lot fewer of everything else. I love the MOTAC function. Also good ones from Primary Arms, Holosun, Bushnell, obviously Trijicon, EOTech and Aimpoint are the premium choices.
The prisms also have a lot going for them but as has been stated, they have some concessions as well. The main selling point is the etched reticle that is not dependent on battery power. Some of us old sticks in the mud still worry about battery failure in the field. I have them in 1x, 3x, 4x and 5x. The 1x is the direct competitor to the red dot. It will have the most generous eye box but it still has an eye box. As magnification goes up, the eye box shrinks. If you're running fast, that is going to be an area of concern. If I'm using a 4x or 5x, I like to couple them with a reflex on a 45° mount for up close, fast work. It's very easy and natural to simply roll the rifle over and switch to the reflex and they weigh almost nothing.
