In theory, they are all the same (that's how they make money by selling "high quality advertisement" to buyers. This means they "guess" what you like to see and send more your way (or you their ways), and show more advertisement that they think you will be more likely to click. Pretty much any free stuff online works this way.
In practice, it all depends on which company and how they make their money. Google will definitely ask you to use the google account and suggests everything based on what you use online (chrome on PC, android phone, etc), same for Amazon and Facebook. So far I haven't seen them suggesting nudity yet, but I do see some NSFW memory in YouTube (within youtube only) and search history from PC into my phone (or the other way around).
Apple does not make most of its money this way, so they have less incentive to sell these data, and they are more likely to charge you money when you buy your phone or medias from iTunes.
Using separate Google account works better than just switching to iPhone, IMO.