Unlike the different runners to recruit and their respective costumes that you can unlock, boards in Subway Surfers actually do more than just give you aesthetic improvement. While the default hover board provides the basic benefit of giving you a second chance to continue running, all other boards have 1 to 2 special abilities.
On top of the huge amount of coins you need to rack up to purchase a new board, however, unlocking their special abilities also cost a hefty amount of keys. Before you go on spending either resource, it is best to read through what each special ability can do so you will know that you are making the right choice of investment. Super speed and double jumps are very much useful in our book, but feel free to choose any combination of abilities that match your taste.