Fridge light is best as incandescent. It is on so little ( unless you leave the door open for hours at a time) that there will be no energy savings over any other lamp. CFL not a thing to use for a frequent switched lamp, it only is warranted to work for around 1000 starts at best, and will never get warm enough to light fully so will either be pink and dim or just dim, both with a short life. LED will work if it is hermetically sealed, but there are none on the market as yet in this application.
You can use the15W lamp in it's place, the oven ones have thicker glass so are less likely to die from thermal shock. The 5W extra will not be noticed at all unless the switch is stuck on and the lamp burns all the time. Check that, most lamps last at least 5 years in this application, often longer than 10 years.