EOR vs PEO for international hires — where's the actual line at 5-10 international employees?

We're 200 EE in the US and just hired 3 employees in the UK, 2 in Canada, 1 in Mexico through an EOR (Deel). It's working but the per-EE fee is high.

At what point does bringing international payroll in-house (or onto a multi-country PEO like Globalization Partners) make sense vs. staying on per-EE EOR? What was the trigger for people who made the switch?