You might like Manymo -- our company -- it's Android emulators as a service. Every recent OS and screen size combo; launches in a couple of second. Accessible from a browser, or in ADB.
The answer is: it depends. This is an android emulator - the same that Google ships with the Android SDK. A real device will probably be more responsive.
You will also have the difference of a touch based interface on a device and the emulated touch interface when using mouse-based devices (Manymo in your laptop/desktop browser.) That said, You can also use Manymo on your iPad...
In any case, having a device with the all screen size and OS version combinations does not really scale. Trying to do that gets rather expensive.
https://www.manymo.com/