N-heptane is better simply because you know what youre using. Naphtha is a catch all term for any mixture of alkanes, cycloalkanes, alkenes or arenes. Light naphtha can contain pentane, which is a CNS depressant, hexane and cyclohexane, which are both chronically neurotoxic, as well as cyclopentane, which has historically been used as an inhalation anesthetic. Heavy naphtha can contain benzene, which is seriously hematotoxic, i.e, damages your bone marrow leading to conditions that mimic leukaemia. It can also contain toluene, which is both acutely and chronically neurotoxic, and causes reduced sperm count in men and reproductive difficulties in women. It can also contain xylene, which is toxic to the vestibular nerve, causing inner ear damage, and damage to the brains balance centre, resulting in loss of balance and coordination.
In my personal opinion, there is almost no reason to use anything but n-heptane. It is easy to get off the internet. It is comparable in price to light naphtha. It is used to clean and degrease metal, so if you have a car or a bike, theres a reason to have it if anyone asks. It is relatively easy to work with, owing to its limited toxicity and high boiling point, so youre not going to fill your room with vapour even if youre working at higher temperatures, but it also has quite a high vapor pressure, so it evaporates quite easily if placed into a shallow dish, and it is also heavier than air so even if you do have an accident, it pools near the ground rather than spreading through the air where you can breathe it in. The one drawback that I see with n-heptane for some people, is that it is not actually a great solvent for alkaloids, so anyone wanting a wider range of compounds may not be able to obtain them with n-heptane.
