Every ERP can be bent to fit your business. The question is what that bending costs you at upgrade time. After years of customising all three, a pattern holds: customise at the edges, never the core.
Sage rewards discipline: keep custom logic in integrations and reporting layers. ERPNext is the most open, which makes it the easiest to break; stick to custom apps and hooks rather than patching core doctypes. Odoo sits between, with a proper module system that stays upgrade-safe if you resist editing standard modules.
Before you sign anything, list the five workflows that genuinely differentiate your business. Those deserve custom work. Everything else should bend to the ERP default, because every deviation is a tax you pay on every future upgrade.
