I think it's ultimately better for Curry to get out of the building to build his resume more. And Buffalo is a really good steppingstone to an OC position down the road that he likely wouldn't have gotten by staying with the Saints.
I hope it works out for Curry, but I still remember the last time Brady tried to create and implement his own offense as an OC and it wasn't pretty in Carolina. He did a great job calling plays for half the year in Buffalo, but being the OC that has to develop and install the scheme is a lot different from just having to call plays in a system that is already designed and implemented. He may well succeed, but it's a question Brady is going to have to answer.