The basketball system you choose should depend on several things including the size of the playing area, level of player skill, player age, and budget.
If you have children in Jr. High or higher, you might consider a full sized 72 inch tempered glass backboard (Pro Dunk Platinum, Diamond). This is the same system that they will be playing on in gyms throughout their playing career. Many people like to emulate the gym setting as close as possible. This helps to improve accuracy and improve their skills at a faster rate. A 60 inch glass backboard (Pro Dunk Gold, Silver) will feel just about the same if you are limited on space. If the basketball hoop is going to be strictly used for recreational purposes, a smaller backboard will suffice (Pro Dunk Silver).
If you have young ones, you might consider an adjustable basketball system. The height at which they play will change until they start playing at regulation (10 feet) in Jr. High.
Most systems are adjustable between 7.5 feet and 10 feet. Some systems allow for younger players to shoot by lowering all of the way down to 5 feet such as the Pro Dunk line of basketball goals.
Players of all ages enjoy lowering the basketball goals down to dunk. Not all basketball goals are warranted for dunking. Make sure to pay close attention to the warranty before purchasing a basketball goal.
Everybody wants something that is going to be durable and last a long time (while still looking good). Premium basketball goals should be considered an investment as they will last for a very long time and can be taken with you when you move*.
If you want a regulation sized court you'll need a basketball system with a 5 foot extension arm. This will completely take the pole out of the playing area. Having the pole out harms way will reduce the risk of injuries and look more professional. If you're spending a lot on a dedicated court you might as well do it right!