It depends from each mod interpretation.
If the duplicated topic is active then odds that the second topic will be deleted are high.
If the first topic is less than 1-2 month old, I recommend to continue posting on it only serious questions.
If the first topic is > 3 months or years old or locked then i will create another one and make a reference to the original one.
If the first topic contains useful informations but it is too old or locked then why don't you merge its contents with some other topics and create a new one containing more informations with reference to the original one. (list of useful information...etc)