The real question (besides quality) is the wavelength the LED. A violet 405-410nm wavelength light will fluoresce most things that show up in UV. I carry a violet Photon keychain light (405nm) and it fluoresces things better than the UV Photon simply because it's brighter (at least it looks that way). The UV Photon is 370nm, which is mostly invisible to the naked eye and does produce very accurate UV color rendition. What I mean is, unlike the violet Photon, the UV doesn't tint things purple, "tainting" them. Like when I shine the tritium vials on my Luminox, they show up the correct color under UV, but under the violet the color isn't quite the true color.
My brighter UV light is a Jil which uses the Cree 7090 UV LED, which is far brighter than the 5mm LEDs in those cluster lights. It's 395nm so it's less purple than true violet, but it's still a very visible purple.
The problem regarding that UV light you have in your link is that we have no idea what wavelength the LEDs are. It also matters what you're intending to fluoresce. If it's just highlighters, UV ink (for handstamps or whatnot), or symbols on ID cards and such, most any UV or even violet light will suffice. Heck, even blue LEDs can fluoresce some things like highlighters. If it's to detect cat **** or scorpions, or other more specialized uses, there's also specific wavelengths that function best for each circumstance.