Assume that you have a couple of ideas that you think are good enough to prototype into demonstrable devices. What option would you take and why?
Option 1 - Build everything from scratch including designing and soldering the circuit, embedded software and finishing / packaging touches. Basically in this option, you do everything and don't source ready-made circuits from elsewhere. For e.g., you can easily get ready-to-use PCB's for power supplies, motor drivers and so on. Instead you build your own.
Option 2 - Figure out the common or readily available blocks in your schematics and source them from third parties. You work on only the parts that you think add value / novelty to your prototype (or one's that aren't readily available). These may include the electronics and/or the software.
There are obvious costing implications but I am asking to ignore those since they are easy to arrive at and analyze against. I am also not touching on obvious IP implications on getting stuff from 3rd parties - again assuming that these are taken care of legally. Also, please sensitize your answers to commercialization of these prototypes - that is, assume that these will be available as custom or off-the-shelf products in the future.