"Surface Mounting" in today's terms usually implies mounting to the copper side of a PCB, which has been a way of miniaturising components and circuit boards. Switches mounted that way, by their nature, must be small with very little operating force and therefore with very little current carrying ability. Through hole switches can be much larger, and are often variations on panel mount types, but with pins instead of lugs to simplify wiring.
Most switches are panel mounting, either poked through a round hole and held by a knurled knut (typical toggle lever switch and the "push-push" type found on table lamps), poked through a rectangular hole and retained by sprung ears moulded into the switch body (rocker switch as found on car dashboards), or they have a flat face panel with a lug at each end for fixing screws (RX slider switch). This last can be dropped in through the front surface or fixed from behind with or without a fascia plate, as is usually the case with the RX switches, which effectively are clamped in their own small enclosure.
Like various posters have said, pretty much any switch will handle 6 volts, the critical consideration is how much current the lighting will take, generally, the bigger the current, the bigger the switch, the more force needed to operate it and the stronger the structure it needs to be mounted on. Unless the contacts are a bit exotic, like having a gold or platinum flashing on the contacts.