Guess it would entirely depend on quite a few factors. Like how big are they? What kind of functionality are you looking for? What kind of Material etc. Its kinda if you say I got a lot of stuff to get from A to B what is the best vehicle. Could be a car, a van, a truck, a tanker if its liquid or maybe an airplane or a freight train

Nylon will be the go-to in this case. You want the material to survive the impact without cracking, PETG, in this case, will likely not survive the impact and crack.

I recommend you to buy raise3D pro2 dual extruder 3D printer as it's more pocket-friendly and inexpensive 7dollaressay website review and for more stability and reliability as you said above go for Ultimaker 3.