Premium basketball backboards come in 4 sizes. 48, 54, 60 and 72 inch backboards. The size of your playing area should really dictate how large the backboard should be. If your going to install your basketball goal on 2 car driveway I'd recommend a 54 or 60 inch backboard. If your playing area is pretty small or your on a budget a 48 inch backboard should suit your needs. If you have a large playing area such as a 4 car driveway or backyard basketball court I wouldn't look at anything less than the 72 inch backboard. 72 inches is the standards NCAA and NBA size.
Skill level also plays a part in selecting a backboard size. Since high school and college use the standard 72 inch backboards many people like to purchase this size to closely reproduce actual playing conditions
I strongly urge everybody to get a tempered glass backboard. This material has several benefits over acrylic. Tempered glass, like the wind shield of your car will stay crystal clear for the life of the basketball system. Acrylic will dull from scratches on the softer plastic material. Tempered glass also plays much better. There is no bow head effect like the acrylic boards.
Acrylic boards are lighter meaning you don't have to buy as large of a pole to support them. They are also considerably cheaper. If your on a budget and still want a good sized clear backboard acrylic might be your answer.
For a complete explanation on the differences between acrylic and tempered glass reference this guide.
All premium basketball goals should have a break-away rim. This means that when players hang on the rim they will give via spring mechanism within the rim. It also makes the rim softer when shotting long shots and allows the ball to go in more often. Some companies offer a 360 degree breakaway rim in contrast to most rims that break-away from front to back. These rims will bend down at an angle.
First, let me define overhang. This is the distance from the front of the pole to the front of the backboard.
What to expect
Most premium systems have an overhang of 3 feet to 4 feet. Some will be as small as 2.5 feet. I'd be leery of these systems as they are probably cutting quality else where as well. Some systems have large 5 foot overhangs as well such as the Hoops Pro Dunk Diamond basketball goal.
On a regulation court, the distance from the baseline to the front of the backboard is 4 feet. If you are building a basketball court and wants to get the dimensions of their court just right. You'll need a 5 foot extension arm. Basketball systems with a 4 foot extension arm are not long enough to get the pole out of the regulation playing area.
A larger overhang means more safety. Players don't have to worry about running into the pole when coming in for a hard lay-up. They also don't have to worry about stepping off of the court and rolling an ankle or tripping over something.
A larger extension will help to always keep the ball in play and not bounce off of the court.
Padding is important on all systems but extremely important if you have children or aggressive players.
Adjustable systems should always have backboard padding if players will be dunking. This keeps aggressive and inexperienced players from injuring their heads when jumping under and towards the goal.
Pole padding will keep players from seriously hurting themselves if tripped, performing a lay-up or being pushed while underneath the basket.
Gusset padding wraps around the base of the system. It is meant to eliminate puncturing, ankle rolling and tripping. Since most premium basketball goals use a pier, this mean 4 bolts are sticking up from the concrete. The padding covers the exposed bolts and protects players.
There are several different types of adjust mechanisms
The hoops Pro Dunk Systems use a reliable easy cranking system that employs springs to do most of the work. Despite what some might think, the springs do not wear out. This is the most tried and true adjustment mechanism. It has been in use for years and is perfected. Some such as the Goalsetter systems do not put tension on their adjust mechanism and believe this makes it last longer.
Lifetime Mammoth systems use a Hydraulic system to move the backboard up and down. On bigger systems this can sometimes look awkward and overbearing. To adjust you squeeze a handle and move your arm up and down unlike the circular cranking motion used with the spring assist mechanism.
Although I have not seen one in person, I have heard that there is such a thing as a push button electric adjust mechanism. No mainstream retailer sells this.
Some companies offer systems that are mostly contained inside the pole. This is to keep users safe from external moving parts.
Most companies use an external adjustment design. This is the tried and true method.
Some companies use cables in their design. We have heard many complaints about these. Ask your dealers how the adjustment system on their goal works before purchasing.
Bison® is the only company left that uses the separate adjustment bar that hooks into an I-bolt high on the system. Most premium systems use an external spring system. The bar is awkward and unreliable. Several small portable systems carried by local stores still use this method.
Many goals have the ability to be padlocked at certain heights. If your worried about your system being vandalized, you should make sure you have this ability. Some goals have gone further and allow you to remove the adjustment handle completely. This seems more convenient until you loose the handle.