I assume you are talking about the benefits of using a fever-reducer, like acetaminophen or ibuprofen, in either a tablet or suppository form. There are also liquid-forms of both medicines.
The answer is: it depends on the age of the child, as well as if they are vomiting, dehydrated and how well they tolerate each type of "avenue".
Our (personal) pediatrician recommends the liquid form of fever-reducing medicine for our 2-year old. He drinks it from a cup (the younger kids can "drink" it from the dropper/syringe provided). When our toddler was a year old and crying too much to take anything orally, our pediatrician recommended the suppository-type. Both types worked within 15 minutes; I did not notice a difference.
I was not able to find any literature regarding "which type works best", as each one has a different dosage (based on if it is liquid form, dissolvable, chewable, suppository, etc). I believe the type that works best is the type your child tolerates best!
Next time I'm at the pharmacy, I'll ask the pharmacist if one type is better than the other, and report back.