The most noticeable difference is still the metal heatsink. LED drivers would be non-isolated ones, so only a single coil (not a transformer). The other part of

The most noticeable difference is still the metal heatsink. LED drivers would be non-isolated ones, so only a single coil (not a transformer). The other part of the weight difference would be capacitors (hopefully larger ones), and (hopefully) input filtering. Some LED bulbs have terrible input filtering (or not at all) and can easily die due to transients (incl. inductive motor noise/kickback) - input filtering normally would be a capacitor + coil. An example of a similar (LED based discussion) a year back: https://news.ycombinator.com/item?id=35371750 https://news.ycombinator.com/item?id=35371750