you are mixing up two different kinds of lighting. The house hold bulbs used with bearded dragon tanks is for Heating, not to provide a UVB source. Hence, you need two bulbs, one that produces a high level of UVB and one that produces heat and light. The UVB bulb you bought is great for UVB. The coiled incandescent bulb that fits in a normal light socket, is I beleive, the zoo med UVB light that recently came out. This should still provide the same level of UVB but what it lacks is it will not cover the same amount of area, thus meaning there is less change your dragon will be exposed to the UVB light.
Having the light near the basking spot will ensure your dragon does get the best exposure to the UVB rays from a coiled incandescent UVB light but personally, I feel you can't get that light close enough to the basking spot without exposing it to the high heat from the basking light which may over heat the UVB bulb or shorten its life (I don't know this for a fact but the logic of it makes sense to me). Thus, having the long tube style UVB lights covers more of the cage, doesn't have to be right beside the heat lamp just close enough it does expose the basking area with UVB rays.
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PHLdyPayne