Q: What is the optimum spectrum to visualize things with? Theoretically, which type of vision would be the best to see things with?

Physicist: At the risk of being a smart-ass; it really depends on what you want to see.

Andromeda, the nearest galaxy to the Milky Way, as seen in the infrared, radio, visible, and x-ray parts of the spectrum.

Different wavelengths are good for seeing different things.  Infrared is good for seeing dust, x-rays are good for finding blackholes, novas, and bones.  You want to see stars and pretty much nothing else?  Radio waves.

So the short answer is that there’s no best spectrum for seeing stuff.  But given the choice, I personally would go with x-ray vision.