Translation:Do you want a hard or soft toothbrush?
Do you want to have would a very literal translation of "Vill du ha". The English verb want as in "to want something" is usually translated as "vill ha" in Swedish. The thing is that you cannot say "vill" without the "ha" in Swedish if it is followed by a noun.
So Jag vill en tandborste IS WRONG But Jag vill ha en tandborste is a perfect Swedish sentence.
To translate sentences like Jag vill ha en tandborste to I want to have a toothbrush sounds like bad English to me and especially since I want a toothbrush conveys everything in the Swedish sentence perfectly.
Actually if you do a Google search English does prefer "hard", but think this may differ from country to country. What you are really talking about -- normally, as we're in the realm of marketing here -- is the stiffness of the bristles (as opposed to the handle, the rigidity of which varies as well). Personally I have no problem with "hard" and "soft", but agree that "firm" might be a better descriptor for bristles than hard/stiff. [http://cosmeticdentistinbocaraton1.aaafinancial.com/are-you-brushing-your-teeth-the-wrong-way/] What I do have a problem with is that DL should accept variants like "a hard toothbrush or a soft one," which to me is the most natural way of posing the question.