Choose a pool vacuum based on budget, desired vacuum filtration system, and convenience. There are four main types of pool vacuums: robotic, suction-side, pressure-side and manual.
Lower cost suction-side and medium cost pressure-side vacuums attach to the pool's filtration system. Suction-side vacuums use the pool's filtration system for all debris, while pressure-side vacuums have a bag for large debris and only send small particles through the pool's filtration system. Both vacuums result in the extra cost of needing to replace pool filters more frequently.
Robotic vacuums are the most expensive option. These vacuums do not use the pool's filtration system and require very little effort to use. Manual vacuums are the cheapest option. They do not use the pool's filtration system, but require a lot of effort to use.