Hi Ash,
Having set up Preference centre in Marketo around GDPR for Europe, we then migrated into a global instance.
The company also has One Trust and I looked at both options in detail.
It wasn't just costs based but we chose to stick with Marketo and enhance the GDPR preference centre to become a global preference centre- covering GRDP, Brazil, Canada, Singapore, Japan, Australia etc.
This can be done in One Trust but would have been an extra cost/service to what we already had, where as in Marketo it was about building the program, and mapping the logic based on country with no extra cost.
Make sure your legal team are one of your stakeholders and provide you with all the legal text and logic.
We also introduced dynamic forms based on country selected to display the legal text and necessary checkboxes.
One of my most favourite projects to work on, as it was truly global and working with multiple country needs. Being in the UK I already had the knowledge around GDPR.