Ultimately it comes down to personal preference.
Typically if you have a lighting fixture, you would try to use an IES light to produce the most accurate lighting pattern for that fixture.
Rectangle lights are good for when large swaths of light are required in one single direction, lots of people use them to simulate the exterior light coming in through a window, or for product renders as studio "softbox" lighting.
Sphere and Omni lights will produce, as the name suggests, a surrounding light, similar to a bare bulb.
My best suggestion would be to make a simple scene and just play with each type of light to see how it behaves.
Robert