Mat-work Pilates can offer huge benefits in overall movement and strength. No special equipment is needed, it's extremely accessible, and this is why Pilates has become so popular in so many markets. However, equipment Pilates - especially when used in conjunction with mat-work, can really take things to the next level.
The various pieces of Pilates equipment act as a support system for the body by helping assist it into proper form. They adds resistance to the Pilates exercises via the use of the springs that form part of the machine, and extra springs can be added to build strength in the bigger muscle groups, or lower springs can be utilised to challenge the stabilising muscles. This means that the intensity can be varied considerably from one person to the next, making everything incredibly versatile. This flexibility, combined with the support afforded by the resistance the equipment provides, allows people of all capabilities (including those with limited range of movement or injuries) to safely complete exercises.
Equipment Pilates is great for rehab purposes too as it allows you to exercise in a horizontal plane of motion and not be vertically loaded and weight bearing through the legs.
For example if you've had knee surgery or a knee injury, this horizontal plane enables you to strengthen the muscles of the leg through a larger range of motion using a lighter resistance than your own body weight, speeding up recovery through controlled movement. Another example is someone with scoliosis: they may find it difficult to do Mat Pilates, but by using equipment such as the reformer, they would be able able to increase their range of motion safely and effectively.