First of all, you really should decide which of the two you are going to oppose in your essay or speech (I assume that is what you are working on here). The arguments against these two activities are rather different.
To argue against hunting, you will probably need (depending on what kind of prey you are talking about) to argue that hunting is an inhumane activity. You would need to argue that it causes excessive pain to the animal that is being killed.
If you are arguing against poaching, the argument is much simpler. Rules are set regarding hunting so as to ensure that the population of the prey will remain stable and viable. Poaching animals is bad because it tends to endanger the viability of the entire population of a given animal in a given area. Therefore, you can argue against it on much more pragmatic and much less moralistic grounds than you can use to argue against hunting.