I would order the 10.0, honestly. My sense is, it's well worth the slight hassle of ordering and waiting. Also, you will likely get the 10.0 on line for MUCH cheaper (even with shipping), than the 5.0 in store. At least, this has been my experience. Best price here:
http://www.petmountain.com/product/...bs/504983/zoo-med-reptisun-10.0-uvb-bulb.html
My own experience with the 5.0, was ok. We had a compact, initially, and as compacts do, it was wreaking havoc with beardie's health. We upgraded to a ReptiSun, and while I would have liked to get the 10.0, I was concerned because our starter tank while longish (2 feet), was quite short (only 9 inches), and I thought the 10.0 might be too much for such a small space. The 5.0 helped our beardie quite a lot, in the beginning, and her appetite was coming back and so on, and we were very encouraged. However, a month in, I felt the change just wasn't dramatic enough, and learning that she could get to within 6-8 inches of the UVB safely, I felt it was time to upgrade yet again. As it turned out, we were able to get our hands on a 40 gallon breeder (thank you Craigslist!), and we went all out and got a TRex MVB, so I never got to compare the two bulbs.
Here on the forum, the consensus is, that the 5.0 is a good bulb, but just 'ok' in terms of the UVB it puts out. Better to go with the 10.0 if you possibly can, for optimum health and growth. In particular, anything you can do to get beardie off to a good start, is always recommended. (Not sure if you have a baby beardie or not, but thought I'd offer that just the same.)
My .02 for what it's worth. :dontknow:
The best,
Em