They mean pretty much the same thing. The only subtle difference is that 'opt' is usually used for non-physical items. "The government opted for the new tax." "He opted for the second retirement plan." "She chose Tom because of his sense of humor." "I'll choose the chicken over the beef." [Note that you could switch 'opt' with 'choose' in any of the above sentences and still be correct] The term 'opt out' means to stop participating in some plan or activity. "He opted-out of the first health care plan." So you can either opt for 'choose' or choose 'opt' - or even opt for 'opt' and choose 'choose'. ;-)