I've flown for years wearing boat shoes, because they give me better traction when preflighting a wet aircraft and on slippery wet decks offshore. I know several pilots who have had serious injuries from falls from aircraft, and even from wet stairs. Almost any shoe/boot can work, it's just a matter of practice, and I think you should wear whatever is most practical considering the non-flying conditions. In the aircraft it's not a big issue, other than comfort on long trips.