A lot of folks really like having the 2 settings since it mimics the original backlit SP as closely as possible, but for my own personal unit I just have it wired up to the brighter setting. I often find the brightness of the original backlit SP to be a bit much, so the toned down brightness is perfect for me. I don't really need the 2nd setting, but I can totally understand why some folks do. It definitely knocks a ton of work off of the installation LOL! The switch is probably the most pain in the butt part of the whole install.
The difference is fairly significant. It's not a huge difference, but it's pretty noticeable. It as pretty hard to capture in photo and video though :/