However relevant this possibly is a court case it is less relevant when you are about to pick between a nexus, an iPhone and a Samsung S-series.

Also while IANAL, note that in a number of jurisdictions EULAs like the ones you seem to think about might not be valid. Norwegians consumer authorities recently mocked them and I applaud them for it.

With a Nexus you're trusting Google with a lot more info than Samsung could hope to obtain. So if this isn't about legality then I'm not sure what it is. Presumably Samsung aren't storing your email credentials so they can launch a spam campaign, and you've not provided anything like enough information to deduce that they're doing anything other than, perhaps, keeping the email moving.

I never read EULAs and I can imagine they're not valid everywhere, but they're useful as a measure of the intent of the company producing them. I imagine Samsung, for example, reserves the right to use any information you provide to ensure a certain quality of service. I'm sure Google have run their EULAs - valid or not - past similar lawyers.

Google has shown that they fire sysadmins who put their nose into customer data even though tje sysadmin in question had good intentions. AFAIK they also have a fairly strong security record. I'm not saying Samsung doesn't but I don't know.