So many choices and yes I have tried them all and in many cases at the same time since certain applications only offer support for one or the other or a couple but never all of them.
In my experience these last few years, dropbox is the clear winner when you want to talk about compatibility. If an app supports any cloud type of storage then Dropbox is always there but (always a but) its also the most expensive of all cloud storage services. I was paying $199/year for 2TB which they just upgraded to 3TB. They really don't offer a wide selection of choices.
I use to use Google Drive a lot but they have been phasing Google Drive out for some BS app called Drive Stream which is part of the Google Suite and that is great if you are a business but if you just want to pay for cloud storage then Google probably won't be your choice anymore. I think its a HUGE mistake on Google's part to decomm Google Drive. It was a direct competitor to Dropbox and the fight was always very close on who won. Right now, Dropbox is still the winner since Google has removed itself and now offers this tool called backup and sync and its complete garbage. Another one bites the dust.
Through the years I have become more and more an Apple fan and then Steve Jobs passes away and I can see and feel how Apple has lost a lot of its drive for innovation and being the leader of new cool stuff. iCloud Drive could be cooler and I expected it to be cooler but its slower than any of the other cloud services and its not always available as an option to store stuff or pull files from. They are also one of the more expensive cloud storage choices.
Since I have an Amazon account and I thought because AWS (Amazon Web Services) is so huge and pretty much dominates the cloud services arena I thought Amazon Drive would be the coolest but its the least accepted cloud storage solution of any of them. I haven't found more than a couple applications that recoginizes Amazon Drive. It could grow but I really don't think Amazon cares if it grows or not. It feels as though Amazon threw it out there for people to use if they want but without any bells or whistles or compatibility.
Now anyone who knows me knows I have a strong dislike for Microsoft. I feel they just buy other peoples inventions, puts the Microsoft sticker on it and changes the code ever so slightly to make it worse than it was. With the release of Office 365 (where if you want to use office products anymore you have to continue to pay a subscription for it) they are slowly getting away from you having the ability to just buy office products which I hate that I have to keep paying for something I already bought. Something nice with Office 365 is they give you 1TB of storage on OneDrive. I was very reluctant to use OneDrive (stupid Microsoft) but since I already paid for it with my Office 365 subscription and its accepted on just about every application I have tried and it works really well with any office apps on my iPhone or iPad, it just makes sense. Now they don't allow you to expand your storage like the others. You are locked to 1TB of drive and thats it (probably because there stupid Windows servers would roll over).
So there you have it.. migrating from Dropbox and Google Drive to OneDrive and keeping some on my iCloud Drive. This saves me some money. Also I do utilize my QNAP NAS as a backup of all my old archive stuff that I don't need in the cloud.