I usually prefer bounced and/or diffused flash to available light for indoor photos of people. In Canada, white balance will be all over the place because home lighting is a mix of tungsten, fluorescent, halogen and xenon. Commercial lighting can be all these and more. Intensity is usually low enough in artificial light that you will need wide apertures, therefore low shutter speeds and thin dof. Under these conditions it's rare to have more than one person in focus. If the subject moves, they will blur. Flash overcomes these limitations. Harsh flash light can be controlled with bounce or diffusion. For close quarters like a house party, I like to use my Sigma 530 Super's integral diffuser with an Omni-Bounce. For a larger event, I like a flash bracket.
Off-camera gives the best results but requires setup and placement of the flash and subject, so I don't use it much. The Sigma flash comes with a handy little foot that lets you stand the flash on any flat surface. The flash can be aimed at the subject, diffused or bounced. I have a light stand and umbrella, but it's for formal photos, which I rarely do. If I'm using the built-in flash to add to the lighting, I mount a Puffer to soften it. I'd like a second flash, but I have very limited opportunities for using it, so it hasn't been worthwhile so far.
One of these days I'll get a Better Beamer for wildlife and bird photography. Flash is a big help for macro photography, diffused or off-camera. The cord for my flash bracket lets me angle the flash, which makes it useful for macro: