its not the wattage that makes it hot. halogen bulbs burn much hotter than incandescent, regardless of the wattage. a 150W fluorescent is almost cool to the touch when on, but i wouldnt go touching a 40W halogen or incandescent bulb while its on, because it would be scorching. i would probably say that an HID bulb, regardless of the bulb type (Metal Halide, High Pressure Sodium, or Mercury Vapor) burns hotter than a halogen.