Let's remember Gmail's primary business model is snooping and selling out customers. Best to not do business with such companies, esp if you have valuable data. Self-hosting was a great idea even before the Snowden leaks made it a better idea.
Actually I trust Google more than anyone else that they do everything they can to keep anyone's private data private. The problem is that that doesn't help when a government agency walks in with a secret court order, be it legitimate or illegitimate.
That's why european end users (and corporations w/ valuable IP) walk away from US based cloud providers or even want to go back to being all self hosted. You can't be 100% sure about your data safety with them and you'll be in deep trouble with your own customers if a data breach - be it lawful under US law, but not under european law - should happen.