I have the choice between a dwarf goat or a miniature pig .Which one should I bought?

A pig is not a pet. It is a garbage eater. Pigs are famous for unclean habits and the only way to clean them up is to keep them in a coop like chickens, and then flush it every day.

Goats are cleaner but they are still not exactly a pet. About the only reason to want a goat is so you can milk it and have fresh untinkered-with milk.