I prefer series wiring for any kind of LED, because circuit elements wired in series share the same current. Thus every device in a series string is guaranteed to have the exact same current running through it, and I only need one current limiting device per series string of LEDs.The fear I have concerning LEDs wired in parallel (recall circuit elements wired in parallel share the same voltage), is thermal runaway. That is to say, one of the LEDs is going to get warmer than the others, then get less resistive, then start hogging most of the current.By the way, you might have noticed, on the COB, on the Chip-On-Board itself, they've got an array of LEDs wired in series and parallel, like the designer was not worried about thermal runaway. But I think the thing that makes that possible, is the fact that the LEDs on a COB are so physically close together they're guaranteed to be in thermal equilibrium with each other; i.e. they share the heat, and they're all very close to the same temperature.