Interesting question. Don’t know about amazon echo but the EV3 brick is a way of learning to program but more about concepts, high level. Raspberry pi has two variants, the zero and the normal pi. It has a huge community with a lot of examples and a lot of OS variants running on the Pi. Arduino has also a few variations. There are a few operatings systems but the rpi is really a small computer while the arduino is more a processor without all the fancy stuff (like HDMI out). I have the Arduino Mega 2560 and the rpi3 in front of me. The Arduino only has a USB slave port (for programming) and a power connector. RPI has ethernet, 4 USB ports and HDMI out, a SD card slot (running OS from SD). There is more, but mainly the OS runs on SD, you can connect a mouse and keyboard via USB and hook it up via HDMI to a monitor and you have a desktop via ethernet able to browse the internet. It is not very powerful, not like an intel desktop but still, it runs an OS with x so graphical user environment. I would choose raspberry over Arduino for these reasons. Since the raspberry is a full computer, doing something with it, like control something (home automation), you will have to learn programming and linux commands if you want to unlock the power of raspberry pi.