There are several good differences. For one inhalants are a group of drugs that aren't actually drugs at all, but household or common substances like paint and gasoline. Inhalants are bad for different reasons as well; there affects are much worse over the long and short run; brain damage, COPD, Toxic overdose, airway burns, extreme addiction, (one of my favorites) Butene is nasty for causing someone to become allergic to their own epinephrine with so much as a step cause a fatal cardiac Disrhythmia. Additionally inhalants are inhaled.
Amphetamines a close cousin of methamphetamin, is actually less dangerous in comparison to inhalants. Most of the time these classes of drugs are prescription medications used to treat anxiety or depression, and you ingest them. Doesn't discount the possibility of abuse or overdose though... To much could iverstimulate your heart also sending you into an arrhythmia.
