Pros:

• Bright images
• Great contrast
• Huge screens

Cons: 

• Not quite as good as OLED
• More expensive than some other tech

Technically, Mini-LED is an evolution from LED LCDs. Both technologies use LEDs to create light and an LCD layer to create an image. The difference is the size and number of LEDs. Mini-LED has a lot more LEDs, and they're smaller. This might not seem like a huge difference, but it's enough to warrant its own entry on this list.

The main issue with "normal" LED LCDs is their contrast ratio isn't as good as OLED. As such, the picture isn't quite as good. Mini-LEDs, like all local-dimming LED LCDs, can improve the contrast ratio by dimming certain areas of the screen so dark areas can appear darker. The problem with that is even the best local dimming zone still comprised a fairly large area of the screen. So a small bright object on a dark background -- a streetlight, say -- would raise the level of the surrounding black area, making it appear gray. While engineers have done a lot over the years to minimize this problem, it persists. It has to, it's just physics.

With Mini-LED, a greater number of smaller LEDs are spread across the back of the TV. In most cases these greatly reduce the size of the local dimming zone, so to a casual viewer the contrast ratio is fantastic. Not pixel-perfect like OLED, but close enough. Mini-LED TVs can also produce some extremely bright images, which can be handy for daytime viewing in brighter rooms. There's also basically no chance of image retention, so for gamers worried about marring their OLED screens, Mini-LED is a great alternative. 

The downside? Mini-LEDs are more expensive than their lesser LED LCD counterparts, but are usually cheaper than OLED.