I think modems with a built-in wireless router are good. Modems with a built-in wireless router are usually good enough for most users if the modem comes with a good built-in router.
Users don't risk buying a router which is not compatible with their modem when the router is built-into the modem.
I think modems which also have a built-in router are good for saving space, and using only one power outlet on a power bar instead of two. You also save a little bit of money by not needing to buy a modem, and a separate router which can be more expensive.
A modem with a built-in router may save a little bit of electricity because they use the same power adapter, front LED lights, and parts instead of needing a separate modem and router for sharing the internet which may use more electricity.
Users don't risk buying a router which is not compatible with their modem when the router is built-into the modem.
I think modems which also have a built-in router are good for saving space, and using only one power outlet on a power bar instead of two. You also save a little bit of money by not needing to buy a modem, and a separate router which can be more expensive.
A modem with a built-in router may save a little bit of electricity because they use the same power adapter, front LED lights, and parts instead of needing a separate modem and router for sharing the internet which may use more electricity.