I'm a mix of both....i mainly use built in apps for mail, maps etc but i've had a gmail address for ages and when i got my iPad years ago before iCloud was a thing i set up contacts and calendar via Google so i could sync my mail, calendar and contacts between my iPhone, iPad and also have them accessible via the web on my home or work PC. I could add calendar entries on any device and the others would get them or add\update contacts and alike. Now i'm in that system its a big job to move to something else. I suspect it wouldnt be too bad for contacts to move but calendar would be a pain because i have 3 or 4 of my own calendars that i use then i subscribe to numerous other sports fixtures calendars and things like that and whilst it'd be fine on my iDevices i'm not sure there is a good option for windows PC.