SaaS starters give you the plumbing every subscription product needs on day one — billing, auth, an admin panel, and a dashboard shell — so you can focus on the feature that makes your product different instead of rebuilding the same infrastructure again.
With this many options in one category, the real decision isn't whether to use a SaaS starter — it's which one actually implements the pieces you'll touch first. Skim past the marketing screenshots and check whether auth, billing, and the admin panel are real or just UI.