How does mass spectrometry differ from other forms of spectroscopy?

Although there are Mass Spec ionization chambers that use soft ionization, which is less destructive sampling, Mass Spec isn't always the best in nondestructive sampling (if you have a cheap instrument that only costs a few thousand dollars), so it's not so bad now! :)

An indirect, soft ionization that fragments less and makes it easier to observe the parent peak(s) is achieved, for instance, in Matrix-Assisted Laser Desorption Ionization (MALDI), where a sample matrix absorbs a laser ionization source and functions as an intermediate body between the laser and the atoms.

Robb G. was specifically referring to electron impact mass spectrum, which is no longer as popular even though electron ionization is more accurate because there is no actual collision.

There are much better Mass Spec ionization chamber variations, like CI and ESI, and there are other kinds of Mass Specs that ARE nondestructive, like Fourier Transform Ion Cyclotron Resonance (FTICR), Time-of-Flight (TOF) spectrometers, and Orbitraps, but they are on the more expensive end of mass analysis instrumentation out there (on the order of $800000~$2000000 for FTICR spectrometers).

Mass spectrometry differs from other forms of spectroscopy in that it measures the mass-to-charge ratio of ions to identify and quantify molecules. Other spectroscopic techniques, such as infrared spectroscopy or nuclear magnetic resonance spectroscopy, analyze the interaction of molecules with electromagnetic radiation to provide information about molecular structure or composition.