Coil and compact bulbs don't give off the correct wavelengths of UVB for a bearded dragon to be able to make Vitamin D3 and therefore process calcium (which is important for nerves and muscles too, not just bones
). They are also notorious for causing eye problems (sometimes it takes a bit for problems to develop, but in those cases the bulb is the culprit).
So, the best/safest bulbs on the market for bearded dragons today are the ReptiSun 10.0 tube (not the coil or compact; also make sure it's a ReptiSun 10.0 and not a ReptiGlo), or Arcadia 12% tube. Any other brand or shape is probably okay for other critters, but not bearded dragons.
Both of those tubes are cheaper online than in pet stores, I think my 18" ReptiSun 10.0 tube was $28 with shipping included
*Edited for spelling/grammar. Couldn't help it lol