Who is more likely to get someone pregnant. a guy that fully came inside? or a guy that pulled out?

Inside: The higher volume/number of sperm in the right place increases the chances of conception. However, pulling out is not an effective method of contraception.

More sperm: It only takes 1 sperm to fertilize the egg but the more sperm available increases the opportunity to get pregnant. Therefore ejaculation inside the vagina is more likely to result in pregnancy compared to the practice of coitus interruptus.