I guess that depends on your software background. If C/C++ is not a problem, I would recommend Arduino. I found it simpler to just upload your program as the sole brain of your MCU, rather than working with a Raspberry Pi with Linux and all the abstractions, devices, etc that goes with it.
I’d recommend starting with this as well. The setup() and loop() model gets you started quickly and can take you through a lot of small projects before you want timers or other advanced features.
Plenty of tutorials and libraries (often “working but not high-quality”) are available as well.
Even if c/c++ scares you a little, I’d still start there (I came from a long c/c++ background, but I’ve seen my kids be able to do it with not nearly as much help as I expected to give them).
Dirt cheap and readily available as well. Clones are fine; you don’t need the name brand Arduino boards.
