The innards of pico projectors are very different from those of portable projectors. The pico category almost universally uses simple single panel LCDs to show images, meaning they’re essentially the same as smartphones in terms of projection power. The really cheap ones are more on the level of a calculator screen. But unlike phones and other LCD-based devices, pico projectors don’t settle for showing images on a small screen, they try to project a large image. But they lack the power and brightness to do that properly. Pico projectors are also essentially useless for good quality outdoors use.
Portable projectors, at least the good ones, use DLP technology, which is related to cinematic projectors and even movie theaters. The mirror-like components and lamps within a DLP-based portable projector have very respectable illumination power, resulting in bright images, rich colors, and flexible positioning. Pico projectors have to be placed very close to whatever surface they’re projecting onto, otherwise the image gets diffused very quickly.
In addition to the light source and projection technology, pico and portable projectors differ in terms of battery power. A good portable projector will go for over three hours on internal battery, while pico projectors can barely do a third of that without having to recharge through a wired power source. Additionally, portable projectors give you extras like integrated, powerful Bluetooth speakers for an all-in-one design. Pico projectors either have no speakers or feature basic, tinny sound.