By Dan Weil While the S&P; 500 has dropped 17% year to date, Visa has slipped only 2% and Mastercard just 5%. Payment-processing titans Visa (V) – Get Visa Inc. Report and Mastercard (MA) – Get Mastercard Incorporated Report have markedly outperformed the overall stock market this year, as consumer spending has held up pretty well. While the S&P 500 has dropped 17% year to date, Visa has slipped only 2% and Mastercard just 5%. With Visa set to report its latest quarterly earnings July 26 and Mastercard scheduled for July 28, Bank of America analysts took the opportunity to offer a commentary a…