McKinsey BA FT offered early interview

Got a targeted email from McKinsey their Business Analyst role, did the Solve assessment, and just got invited to interview. They're offering an early slot in July, OR I can wait for the regular timeline that starts in late August. Need to confirm by tomorrowwhich one I want.

Problem is I have basically zero case interview experience right now. If I go early I'd have about a week to prep from scratch — frameworks, case math, the whole thing. If I wait for fall I'd have actual runway to prepare properly.

I know McKinsey generally doesn't let you reinterview again for a while if you don't pass, so this feels less like "sooner vs later" and more like "one shot, when do I take it."

Anyone been in a similar spot? Does the early slot actually carry any advantage (less competition, etc.) or is it basically just about walking in prepared? Trying to figure out if I'm overthinking the "early = better chances" assumption