1) The challenge "suit or tuxedo" has rather obvious solution: tuxedo is more formal type of suit, and it is used only on special occasions, that's why the only reason for this suit getting is if you need tuxedo for your further life - in professional sphere, for instance; or if you just like it inexplicably. Otherwise, tuxedo will be only throwaway. However, at the same time, this choice may help in making another decision - buying or renting. This is the case, because mostly tuxedos are rented, not bought. Suits are more usual attire for a groom and less formal.

2) Buying or renting for the bride's wedding gown is not even the question of price, because this gap is not very significant, but the question of personal desire and common sense. If you don't plan to share your gown with your future daughter (if there will be one), there is no sense in keeping it.

Women's Suits - catalogue;
Men's Suits - article and links to the groom's attire sites.