My general advice is this: get to $1m ARR whatever, it takes.
And just improve what is working to get from $1m to $10m ARR as efficiently as possible. Don’t chase shiny pennies, or new verticals. Don’t do anything in this stage where you have 0 customers or 0 traction. Wait to enter brand new spaces at $10m+ ARR.
So … if as you come up to $1-$2m in ARR, you’ve already almost accidentally entered more than one vertical — with real, paying customers — stick with it. Do both.
But if you are only in one vertical at $1-$2m in ARR, even if you theoretically could be in many — don’t get distracted. It will dilute your efforts and drag them down.
The best case study here is public SaaS Unicorn Veeva Systems. Veeva does Pharma CRM. The original vision was to do Vertical CRMs for many industries. But Pharma was so big … they IPO’d without ever leaving that vertical.