For portable generators, I have always used Honda, they are quiet, fuel efficient, and provide relatively stable electric current (less surging as the load increases), and extremely reliable.
For a full home stand-by generator, I chose a Kohler. We installed it 4 years ago. It has been very reliable also. One of the keys is not putting too much of a load on the generator. Lights, TV’s, refrigerators, and freezers do not draw a heavy load of electricity. Ovens, dryers, furnaces, hair dryers, space heaters pull a lot of current.
you need a fuel supply also for a portable. A good sized Honda portable will burn about a gallon/hour. You have to plan for fuel consumption. You also need spare oil filters (if applicable) and oil. Will need to change it every 50-100 hours depending on manufacturers recommendation