A dedicated IP is an IP address that only one sender uses. Every email from it is yours, so its reputation depends on nothing else.
When it helps
For high, steady volume, usually hundreds of thousands of emails a month from an email service, a dedicated IP lets a careful sender build a reputation that nobody else can damage.
When it hurts
- At low volume, providers don't see enough email from the IP to trust it.
- It has to be warmed up slowly and kept busy, or it goes cold again.
- Any mistake is entirely yours to fix, with no shared good reputation to soften it.
For cold email
Cold email from Google Workspace or Microsoft 365 mailboxes goes out from the provider's shared IPs, which are well looked after. What you build is domain reputation. A dedicated IP rarely makes sense for cold email.