Bulb for my curio cabinet
The 50PAR20 is a 50-watt bulb.  The halogen is 38W, so the total heat dumped into your cabinet will be less.  However, the halogen bulb itself will get a lot hotter than the PAR20, so if the bulb is enclosed (e.g. behind a translucent lens), you probably shouldn't use the halogen.  Further, if the bulb sits close to wood or other flammable materials (and theres' no metal liner to the socket area), you probably don't want to use it.  Even if it never leads to smoke, it might age the wood around the bulb.