Given Google's standing policy of requiring a search warrant for access to user confidential data, as detailed in their Transparency Report[0], my reading is that law enforcement needs to go to the same legal effort to access your data-at-rest stored with Google as they would if it were stored offline in your own house. (And results in the same level of notification to you, modulo NSLs, which are a practical worry for some groups but not others.)
Google can change or ignore its policy at any time, without telling you. Depending on your level of risk, you might not want your security to depend on someone else's goodwill, especially someone for who has very many, much larger concerns than you.
Will Google forgo massive government contracts to protect you? Risk expensive lawsuits? What if you are politically unpopular; will Google risk its reputation for you?
[0]: https://www.google.com/transparencyreport/userdatarequests/l...