The verdict
These tools aren't really competitors, they're treatments for two different diseases, and the honest answer is to diagnose yourself first.
If your inbox is a slot machine you pull thirty times a day, the problem is the habit, and Inbox When Ready is the cleaner fix. It removes the trigger entirely: no inbox on screen means nothing to react to, and you process mail in deliberate batches. It's nearly free, installs in seconds, and never touches your mail on a server. The catch is its reach, Gmail in a desktop browser, full stop. No phone, no Outlook, no AI.
If you're buried under genuine volume, the problem isn't willpower, it's signal-to-noise, and that's exactly what SaneBox automates. Its AI triage files the newsletters and low-priority mail out of sight so only what matters lands in front of you, and it does this across Gmail, Outlook, Apple Mail, IMAP and Exchange, with a mobile app. You pay for it, there's no free tier, and you have to be comfortable letting it read your mailbox.
For most lean founders living in Gmail on desktop, start with Inbox When Ready, it's free to try and the habit fix is the higher-leverage one. Reach for SaneBox when the daily count is the real enemy, or when your email lives across clients and your phone. Running both is a legitimate, if pricier, endgame.