For most pesticides at least, you are going to get two different products depending on whether you vape or combust.
Take DDT (C_14 H_9 Cl_5) for example, it's no longer used, but it's a good representative molecule for organochloride pesticides. Under combustion conditions, the molecule decomposes into CO2 and water, with a little carbon monoxide and soot as well (incomplete combustion due to lack of oxygen). The chlorines in the original molecule will produce chlorinated products. Likewise for organophosphate pesticides except you will get phosphoralated compounds rather than chlorinated.
Under vaporization conditions a few things can happen. If your pesticide is like DDT, it will have too high of a boiling point to be vaporized. If it is like the organophosphate malathion, it will vaporize, and you will be inhaling pesticide. The last option is that the vaporization temp is above the temp where the pesticide decomposes and you inhale some different products.
So, vape is the way to go because it has the possibility of not producing harmful products. With combustion the products will be harmful for sure.
tl;dr: Under combustion you will definitely produce carbon monoxide, soot and chlorinated, phosphoralated, or otherwise dangerous byproducts. With vaporization, you may produce harmful byproducts, you may vaporize the pesticide itself, or the temperature may be to low to affect the pesticide, leaving you safe.