People may say that Windows Phone is a bad operating system because it has few apps and it is even abandoned by Microsoft itself. And Android should be good, but it is not so simple. Having switched to Android from Windows phone, there are some things I now miss.
The first things I appreciated from Android when coming from Windows Phone are the number of available applications, more precisely, the number of open source applications that are available. F-droid, the repository for all these open source applications is quite good, and even though you may not find everything, almost all my apps are coming from there.
Moreover, when with Windows Phone I felt I had a quite smart phone, with Android I feel like I really have a computer. I can do everything I do with a computer, even using the terminal!
Windows Phone interface
Now, there are also things I liked in Windows Phone. The Windows phone interface is really nice, simple and efficient. As the background is black (you can also choose white, but most people don't), on a LED screen black pixels are off so it saves on battery. Furthermore, the app list is ordered alphabetically, which means, you can simple press on a letter to choose the first letter of the app name and you can easily find the app you were looking for.
With Android, I'm always searching my apps because they are on several rows and columns. I know you can perform a search across your apps, but it is simply not adapted to a list of apps in my opinion because it is too much: you have the usual complete keyboard with little buttons which comes out whereas on Windows phone you have just big buttons for the app's first letter.
Windows Phone stability and performance
In Windows Phone, the system and usually also the apps are quite stable and well developed. You know that Windows Phone hardware is usually less powered in comparison to Android phones (less number of processor cores, less amount of RAM), but it still works pretty well even with 3D games. On Android it is now going very high on hardware: do you imagine that the latest Samsung's Galaxy Note 7 as eight cores and 4Go of RAM?!
As Windows Phone's software had really been well designed, it could run flawlessly on cheap hardware and without major bugs. During the three years I had the Lumia 930, I only had about three times weird crashes which obliged me to do a hard reset of the phone which is like rebooting it.
On the Lumia phone I had, it was shipped with lots of Nokia's software and it was very good. Especially Here maps which was a good GPS. Sadly, Nokia is not very active anymore on mobile since its mobile department has been bought up by Microsoft.
Migrating from Windows Phone to Android
I had quite some difficulties to migrate my data to Android, but I found a nice tutorial to export SMS.
Matteo Contrini explains how to export messages with Microsoft's "contacts+message backup" Windows Phone app, then to convert the XML file where are stored the messages with his Python script from Github and then to import the messages with "SMS Backup & Restore”
For the contacts, I chose to import them on my OwnCloud server and then to synchronize them with the DAVDroid tool on my phone.
I lost some MMS in the process because they are not managed by Matteo Contrini's Python script, but I don't mind because I didn't have much of them.
Well, I'm happy to now use Android, but Windows Phone wasn't as bad a people may say!