Since I make most of my own circuits, I tend to go as simple as possible. For non IC circuits, I use a 3VDC setup. Most LED's bias between 2.2 and 3VDC. For circuits containing IC's, I use 6VDC since most IC chips run on 5VDC. This reduces the amount of resisters needed to drop voltages( which create unwanted heat in your model) to the voltage levels for the IC's/LED's. This also gives the IC's/LED's a better chance of surviving should a resister fail with a short. I posted two photos of my Falcon, which runs on a 3VDC circuit. I have dedicated resistors to each LED to distribute heat evenly and protect the LED's individually. My design is meant to last a very long time. The total cost to make both circuits was less than $5. as you can see, the circuits are very bright.