if you're referring to aluminum electrolytic caps, there's no real benefit to smt, other than you save a few holes from poking through your layers. they aren't any smaller than their leaded ancestors, and they're feeble too. their large size and relatively small mechanical connection make them easy targets to get nocked off a board.
you should be able to find tantalum caps from any good distributor, but the high capacitance and high voltage ones are darned expensive.