extraction or root canal? which one hurts less?!

Im 15 years old and my back molar seems to have a really bad cavity or something. Im going to the dentist tomorrow and am very nervous. I have a really low tolerance for pain and have always been scared of dentists. Anyways..the back molar, its the last tooth on my lower left side(my wisdom teeth still haven't come in yet) and it has a really huge deep hole in it. It causes severe pain. the pain usually comes in really sharply, and it makes the whole left side of my mouth hurt, like all my teeth on the left side become sore and start to hurt really badly. Im not really sure how deep the hole is but i think it may be down to the gum. Dentists have always commented how healthy my teeth are and ive never had a cavity or any kind of dental problems in my life, so im really scared. The other day the pain was so bad, i was about to go to the emergency room, but instead we got in touch with the emergency on call dentist, all the dentists in my area were closed that day. The On call dentist prescribed me to antibiotics right away(for an infection i think) and he said that id probably need a root canal or extraction. which one would be better and cause less pain. I am really bad with needles, pain,blood and everything, dentist really scare me. Im going to a sedation dentist that should help me..hopefully! and i might have to use general anaesthesia. I also have sever crowding and my orthodontist said that they would probably have to do some extractions done. what should i do? which one will cause less pain?