If I am in a band where the guitar players has a four 12 cabinet and the drums are loud on stage, then you need and want a four 10 cabinet so you can hear yourself better.
For those who don't like larger combo amps that are so heavy, the separate option can be a better choice. Carvin and many other company's heavy light heads and four 10 cabinets that are under 78 pounds.
For those who want more options the separate system is better. You may have a two 10 cab that might be perfect for a coffe house gig. But at a large wedding reception you may want to use a larger speaker cabinet. So the sep system can be more flexible.
For those who don't like larger combo amps that are so heavy, the separate option can be a better choice. Carvin and many other company's heavy light heads and four 10 cabinets that are under 78 pounds.
For those who want more options the separate system is better. You may have a two 10 cab that might be perfect for a coffe house gig. But at a large wedding reception you may want to use a larger speaker cabinet. So the sep system can be more flexible.