It depends on your experience and development goals. for starting and fiddling around the Pixhawk reference frame like HEXSOON EDU450 would be a nice choice or even good old DJIF450 kit simple and nimble and let you focus on the programming. However, you will realize that flight time and payload will be a limiting factor. So if your development goals include playing with different payloads/sensors or companions computers…etc then I would prefer a larger HEX like tarot X6 for example with a good balance between endurance and payload capacity.
Also, in my humble opinion which could very wrong! I think mastering simulation skills and STIL stuff is an essential development skill that must be in your arsenal.
I’m sure the Ardupilot gurus will have more to add…
It’s in the micro uav size class, it can operate indoor and outdoor, it’s fully Ardupilot supported, modularity it’s one of its main elements with several add-on boards and all the useful pins are exposed for complete customization.
We develop it for ‘real world’ application, to be able to test simulation in real scenarios with the real tools, in our case swarm application in urban space.