My new Logitech G500 goes up to 5700 DPI, but I've heard lower DPI is better for more precise movements, so I have a question... Would 5700 DPI and 2 sensitivity be more precise than 1600 DPI and 5 sensitivity, assuming that both settings move the mouse at the same speed. The thing I really want to get rid of is the mouse jagginess - I want real smooth mouse movement, like the mouse smoothing option in FPS's, but real instead of artificial. So would upping the DPI and decreasing the sensitivity help, or do they just cancel one another out? Also, what settings do you all use with your gaming mice, including weight? Thanks.

5700 dpi means your mouse can move 5700 pixels per 1 inch in any direction. Setting it at this would obviously be way too fast for most things, so the idea that a higher DPI setting is better for accuracy comes from how your computer scales down that DPI through the sensitivity settings. If you have low DPI, you use your computer to multiply out your movements with the mouse, thus increasing how fast it can move. However, minor errors in direction/movement can occur with low DPI settings, so all the computer is doing is multiplying out these errors, thus losing accuracy. Therefore the opposite is true for higher DPI settings. The higher DPI settings allow for more precise readings sent from the mouse to the computer, and the computer then scales these down, without any errors, to a speed you're comfortable with.
 
To be perfectly honest though, I don't see much of a difference, and the only real benefit I see for gaming mice is the DPI switcher. I have 5 DPI settings I can define to switch between. Mine are set at 4000,2750,2000,1500 and 125. Combined with my computer's sensitivity settings, I use 1500 or 2000 on the desktop, and usually the same for games, though again this can change depending on how the game scales the sensitivity as well. I tend to switch to 4000 if I need to speed something up that the game has intentionally slowed down - such as moving a tank turret around faster than usual -, and 125 for something like slow, precise sniping.