Ask HN: Thoughts on bring-your-own Account integrations?

Hey HN, I'm curious what people here think of product integrations in SaaS tools where you bring your own account, versus the SaaS tool just providing the integration themselves and charging for it. As a firm example: Say a SaaS provides SMS functionality: You can either supply the SaaS your API keys to Twilio, or use the SaaS's own SMS provider. Which do you prefer, and why?