On my Nexus I have Dropbox and Google Photos both set to automatically upload images when I'm on Wi-Fi. When I want to "archive" a photo, I transfer it from my smartphone to my laptop using Bluetooth.
Here are the actual images:
To my untrained eye, the images are visually indistinguishable.
But the files are different. Here're the details as I observed. (complete data at the end of the post)
Dropbox: 2015-12-16 16.12.47.jpg
Google Photos: IMG_20151216_161246.jpg
Notice that not only does Dropbox rename the file but the implied date/time is different than the other methods.
Google Photos: 1,557,928
This is using Google Photos "Upload size" set to "High quality", not "Original". In this test Google further compressed the image by 40%.
The other characteristics and metadata are all the same as far as I can tell.
So what am I going to change?
For me each of these tools have different use cases.
For Dropbox, I really like having my images automatically stored in a Windows file system. There's probably some method to accomplish this with Google Photos but it doesn't just jump out at me. I really don't like that Dropbox renames the files.
Bluetooth is clearly the geek's solution. I only use this method when I want to preserve a high quality image. The file system target for the Bluetooth upload varies by whether the file is an image or a video. I probably could change that.
Google Photos is the slickest tool. It's fast and easy to manage. Using "High quality" (which really isn't high quality) is free. I wish that Google wouldn't recompress the images when they fall below 16 megapixels. Since my camera is 8 megapixels I tried changing the "Upload size" to "Original" and sending the image again. I had the same result of additional compression. There are still some outstanding questions to me about this. How long does it take to Google Photos to recognize and act on this Settings change? Does this Settings change on the phone propagate to the web uploading? I'll keep playing with this.