The 5500k are a very crisp white. They are about as far up the scale as you can go before they start to appear bluish. If you looked at them then at a 4300k the 4300(BMW stock are 4350k I believe)would appear to have a very very sligjht yellow to it. I noticed it only wheni had one of each in the car.
I dont like to go any higher up the K scale because as you go higher the light starts to appear bluish and the bluer light screws with your eyes depth perception abilities.