A few months ago I made some of my own reflectors out of aluminum siding. Ideally, you want each bulb to have it's own reflector, something like the second picture. If not, then some of the light just bounces back and forth between bulbs. I'm sure either will work fine though.
A good reflector is made of aluminum. A very good one will have the aluminum highly polished, like "Miro 4" aluminum. A good reflector will show you an extra bulb on each side of the real bulb when you look at the bulb. A very good one will show you 2 extra bulbs on each side of the real bulb. A reflector shaped like \_/ with the "wings" angled to show you an image of the bulb on each side, made from barely polished thin aluminum doubles the light you get from the bulb. The very good reflectors give nearly 3 times the light.