The Roof prism system requires more complex technology to manufacture, and is smaller allowing it to be housed in a straight tube body so it is more compact and lighter. The major disadvantage of the Porro system is they result in larger and heavier binoculars. Porro binoculars are said to provide better contrast and are cheaper.
Binoculars are described using two numbers -- the first number represents the amount of magnification (provided by the eyepiece) and most common choices are from 8X to 15X. Bev and currently have 10X binoculars but she also loved her 8X set (she wore it out) because it was small and light. I find 10X to be fine, but if you’re avid birders you may want more magnification).
The second number represents the size of the lens at the far end of the binocular, and is the collecting objective that “captures” light – larger is better in low light situations and is also heavier. Not a problem on safari’s as you’re riding around, but may be a problem if you’re a hiker.
Bev and I currently each have 10 x 32 (Roof) binoculars from different manufacturers and with different prices