What's the difference between a 2-cycle and 4-cycle gas trimmer?

Two-cycle engines run on a gas-oil mix and are lighter, which is why most pro-grade trimmers here use them. Community commenters on r/lawnmowers point out that 4-cycle engines run cleaner and skip the fuel mixing, but have an oil pump that can starve the engine if the tool is run sideways or upside down. Most reviewers prioritizing power-to-weight for trimming stick with 2-cycle.