The best roof is not the most expensive one. It is the one that fits the home, the climate, and how often the owner is actually there.
Use lifespan honestly
Standing seam metal typically runs 40 to 70 years, natural slate can exceed a century, and quality composite carries warranties in the 40 to 50 year range. On a property you visit a few times a year, the longer service life is usually worth more than the lower sticker price.
Plan for snow behaviour
Metal sheds snow quickly, which is an advantage for load and a hazard for whatever sits below. Entries, decks, and landscaping need snow guards planned in. Slate and composite hold snow longer, which shifts the question to structural capacity instead.
Weigh the structure, not just the surface
Natural slate is heavy enough that older framing sometimes needs reinforcement. Composite mimics the look at a fraction of the weight, and metal is lighter still. This is often the constraint that decides the material before aesthetics get a vote.
Think in systems
Underlayment, ventilation, flashing, fasteners, and installation detail usually decide performance before the surface material gets any credit. A well-detailed mid-tier system outlives a premium material installed carelessly.