We haven't measured provider by provider success rates here, so take this as reasoning rather than data. In our own account work the brand of the mailbox mattered far less than three other things: whether verification arrives reliably, whether you'll still control that address in a year, and whether fifty accounts share one pattern.
That last one is the part people skip. Registration signals get correlated, so a batch using the same provider, the same naming shape and the same recovery address is easier to group than to hide. Vary the pattern before you vary the provider.
The recovery angle matters more than the creation angle anyway. The mailbox is what brings an account back when something goes wrong, so a throwaway that quietly expires is a problem you meet months later rather than today.
Best,
Floqal