Yeah, it is very important to consider how dependant you are on third parties. At the very least the more dependence the more power they have over you. But also how screwed you are if they just go under.

• If you use SaaS they can interrupt your use at any time and you can only react (for example demanding a reversal or lawsuits).
• If you host closed source software they can’t interrupt service on an existing contract but can legally require you to stop using it if they don’t renew the contract. (And if the company goes under you can likely get away with using the software as long as it doesn’t need code fixes.)
• If the software is open source you can continue using the software indefinitely including making code fixes. (Maintenance may be expensive as it is now your problem but that can be costed and an exit plan made if required.)