Lawyer fees, which is better paying by the hour or on contingency?

I have a question that requires good, solid advice. Lawyer A does not charge a retainer, does not work on contingency, has a flat rate fee of $250 an hour, you can use them as often or as little as you like but of course the more you use them the higher the fees, which are billed monthly and they require reimbursement for all travel and food expenses. Lawyer B works on contingency and they will charge 25% of the entire settlement. Of the two which would be the better lawyer from a financial standpoint. The case they would be working on is racial discrimination against a person's employer. Both lawyers have similar strategies so would likely achieve the same results but in the end who would be the most affordable?