Making an evaluated decision is the right decision
In a large enterprise with multiple business areas, there are usually different business/workflow needs. The question of whether to integrate existing processes or absorb into the enterprise ERP infrastructure often appears to come down to short term budget £££ and potential to disrupt or change existing business process (always seen as risky for management) rather than a weighed evaluation of the pros/cons. IUMHO, any evaluation of an ERP path which aligns with business need at the time and guestimated expansion is the right choice as it will lead to a more coherent business and all the associated benefits.
RE: The SaaS offerings - fantastic instant gain for businesses which align closely with the product's own functionality. Not so good once you evolve and/or are forced to do most of the things you need to do outside the cloud.