There's also one other service that isn't Google, or Apple.
I've used Dropbox for years. Works on both iDevices and Android. Take a pic, automatically backs up at full resolution to the Camera Uploads folder. Since Dropbox works on both Mac and PC you can go into that folder very easily to get photos. No having to be online. Makes it very easy to take a pic with my phone, then turn around and post that pic to this forum from my Mac - because the photo has uploaded to Dropbox and thus appeared on my Mac.
And old versions still work. For instance, I have Drobox on my iPhone 6s+ which is running iOS 9.0.2. Still works, still uploads pics, still sees everything I've done in Dropbox with my other apps.
The advantage for me is not having to figure out iCloud Photos, which does not sync to my Android or PC computers. I also don't have to content with compressed images that Google Photos uses in order to have unlimited storage. Google Photos, also, is always trying to classify my pictures and store them in a way it wants to. Dropbox doesn't do that, it just uploads new pics and that's it.
Of course, you're limited to how much storage you have with Dropbox, but you can always empty out the Camera Uploads folder.