Aside from the sharper graphics, VR support, multiplayer with other types, the DLC campaign etcetera there isn’t anything that the new black shark can do that the old one could not, as far as I know. If you still fly the old one and are capable of looking past the dated graphics there is no reason to hurry to upgrade to BS2.
Looking at the current strategy with the A-10C upgrade (and presuming you harbor any interest in some day owning BS3) the cheapest strategy to get it may be to grab BS2 in an upcoming sale and then upgrading to BS3 once that has been made available.