Par 36 and Par 46 bulbs only differ in diameter. The bulb number itself determines the focal pattern on the front of the lens. Problem is that there are lots of numbers, and there is no distinct way to know exactly what the difference is unless you have them side by side. As for the terminal configuration, it seems that was up to the manufacturer, since I have found some bulbs that have screw terminals, and others with the same part number, with push on terminals, and in one case, the bulb had both push on, and screw terminals. I will try to get some pictures to this thread soon, of what I have.