I consider myself an app junkie, but when it comes to my Lumia 640 or my Galaxy S7, I always end up choosing the 640 as my daily driver.
Sure the Galaxy S7 has tons more apps. I can pretty much find an app for anything on my S7. There are some definite advantages over the 640. But one phone cost me $40 the other was a insurance replacement for my Galaxy S5 so it actually only cost me $100 but normally it be around $700. The Galaxy S7 works bueatifully with one of my car phones with Pandora. It has a nicer camera that can shoot better pictures and video and has more cool features. It has any app I want.
The downside is that it heats up a lot of the time, the battery life sucks, the reception at my workplace is much worse than my 640. I can hardly use it at work.
The Lumia 640 has some advantages, in that I can receive my text messages in any car, where they are read to me and I have the option to respond back by voice. Its not a hassle to use and the battery life is really good. I can use my voice to send text messages and the Windows Mobile will add the question mark to my sentences automatically. The map program and camera features have improved a great deal in the last year. Actually some companies have added apps back that had pulled them a year ago. Bank of America, there are new games that were not there last year too.
Amazon added a new app after pulling its old one.