I think the right size of any security engineering team is largely determined by the diversity of threats it has to defend against. Same for the legal team.

So team size alone doesn't convince me one way or the other, even if I were to completely disregard all privacy issues.

I am a Gmail user as is my company, so I do trust them quite a bit. But I feel that Google has a much bigger problem on its hands than Protonmail. Both because of its business model and because Gmail does things like search and spam filtering, which Protonmail cannot do.

[Edit] Protonmail actually does spam filtering.