Can't really speak to that since I never had the v3's. According to LUX the v3's are now the second brightest LED upgrade that you can get, after the v4's. The v4's now use double the LED's that the v3 used so I am assuming that they are significantly brighter, but it could be to support the selectable color as well.

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2011 X5 35i Space Gray/Black Nevada Leather w Dark Bamboo Trim
Convenience Pkg/Running Boards/Cold Weather Pkg/Comfort Access
3rd Row Seating/20% Tint/Style 215 wrapped with Toyo Proxes ST II/ LUX v4

2001 X5 4.4i TiAG/Grey Leather-Retired
djbock's Custom X Page!