“Radically different banking.”
"Radically different" requires the visitor to figure out what's different. The sub-hero does the work, but the H1 should be more specific. A founder evaluating Mercury vs. Brex vs. SVB needs the differentiator in the first sentence.
“"Business banking for startups — built like software. No monthly fees, API for every account, FDIC-insured up to $5M."”
Names the audience (startups), the design philosophy (software), and three concrete benefits (fees, API, insurance ceiling). Each one is a defensible claim Mercury can back up.