The large lump on the back of the LED, plus cable, plug and socket. Plus driver module on some versions which makes things rather cramped in the headlight bowl, and instructions say to keep wiring away from the heat-sink (the black ribbing at the base):

Both headlights were photographed at the same time and Photoshopped together - LED on the left and halogen on the right (as if you needed me to tell you that). They have the same exposure and aperture as demonstrated by comparing the pilot lights at the bottom ... which look particularly awful with the LED. It shows how the correct alignment is obtained by looking at the edges of the light compared to the lines on the glass. Although the LED is obviously whiter it is barely any brighter as there is relatively little 'burn out' of the lines in the glass compared to the halogen. Also showing the 'dead' area at the top, not present on halogen:

Reflection, with another dead area at the top and just right of centre, although at least that will be facing oncoming vehicles:

In the final analysis even though they are visibly whiter I dispute that they are any better in terms of illuminating things for the driver - I couldn't see any improvement in illuminated distance blocking first one then the other, and with the dead area in the middle may even be worse. Basically it is only the colour temperature that has been changed. And as my insurance company rejected them I returned them for a refund, which was quibble-free.

These from Moss are pretty-much the same despite being a different type. More stuff to get in the bowl:

But again no brighter only whiter (look at the pattern on the glass) albeit slightly less dead area at the top: