One of the first and most important decisions that you will probably have to make before you purchase your basketball hoop is whether you are going to get an in ground or a portable unit.  
Here are the most important things you should consider when making this choice.

Stability

Hands down, the most stable system are in ground basketball hoops.  So if what you are really concerned about is having a really good rebound when you bounce the basketball up against the backboard, then you should opt for a permanent  system.  Since these are stabilized by concrete in the ground, they are just sturdier and are able to take a lot more abuse.  
If you absolutely must have a portable system, but still want to get as stable a basketball hoop as possible, look for a portable basketball hoop with the biggest base, and fill it with sand rather than water.  Because sand it heavier than water, it will result in an overall most stable system.

Assembly

If what you are really concerned about is ease of assembly, then portable is a good choice. In ground units, while they are extremely stable, they also require you to mix concrete and perform extensive assembly.  Portable units are usually much quicker to install, and can have you 
If you want to have all the benefits of an in ground unit, but don’t want to do some of the dirty work yourself, you always have the option of hiring someone to assemble and install the unit for you.  Almost any local handyman or fence installer is well equipped to handle that for you for a small fee.

Durability

Generally, adults are a lot rougher on their basketball hoops than kids, so if you are planning on adults using the hoop for the most part, then you should lean towards an in ground system, just because they tend to be able to withstand a lot more abuse and still wind up looking good.  In ground units also typically have longer warranties that cover more, so you can be more assured of the quality.

Homeowner’s Regulations

Not all homeowners regulations allow for the installation of an in ground basketball hoop, so you should definitely read over your HOA agreement before you purchase a hoop.  If your community doesn’t allow for a permanent hoop, then your best bet would have to be a very easy to move portable unit.  This way, you can roll your basketball hoop outdoors when you are ready to play and roll it back in the evenings when you are done with it.