This is Blockbuster 8 Reflector is a great reflector especially for square areas. One of the highest rated reflectors for efficiency and it is affordable. I own 2 of the 6″ blockbusters and they run very cool and are top quality.
The only difference between these 2 grow hoods is the size of the vents. The size of the reflector is the same and so is the amount of light they put out and their footprint.
It is generally recommended to use 8 inch ducting for 3 or more lights in a series. I can tell you these hoods run very cool. If you live in an area that gets very hot you might want the 8 inch blockbuster even if you are running only one. Of course a lot depends on the exhaust fan you use with them.