The biggest trade off is between colour and actual light output. The colour as said above is measured in Kelvin and the light output is measured in Lumen. Now where the trade off comes in is the higher the Kelvin or the better the colour the lower the Lumen becomes. This is also where the difference between OEM bulbs and cheap ones come in. The OEM bulbs can have the same Kelvin rating as a aftermarket bulb say 6000k but it will have a higher Lumen output so the actual amount of light will be higher.
A quick reference is given below:
Philips OEM 4300k D2S bulb:
4250k, 3200lm
Philips Ultinon OEM 6000k D2S bulb:
5800K, 2600lm
Aftermarket 5000k D2S bulb:
5000k, 2800lm
Aftermarket 6500k D2S bulb:
6500k, 2200lm
Aftermarket 8000k D2s bulb:
8000k, 2000lm