If a domestic industry is only surviving because of tariffs then it will lobby to keep the tariffs high and for the tariffs to be effective in sustaining the domestic industry they'll have to be enough to deter domestic consumers from patronizing foreign competitors when domestic producers are lacking. That means domestic customers get screwed and domestic companies don't have the incentive to improve as long as they can successfully lobby for continued tariffs.
If you only provide subsidies then consumer prices go down rather than up because the mechanism of operation is for the subsidies to make the domestic supplier more attractive rather than for tariffs to make foreign suppliers less attractive. Meanwhile the subsidy is paid by the government and then the legislators will be trying to keep it down rather than raise it because it reduces the money they have to spend on other things rather than increasing tariffs which do the opposite.
If you only provide subsidies then consumer prices go down rather than up because the mechanism of operation is for the subsidies to make the domestic supplier more attractive rather than for tariffs to make foreign suppliers less attractive. Meanwhile the subsidy is paid by the government and then the legislators will be trying to keep it down rather than raise it because it reduces the money they have to spend on other things rather than increasing tariffs which do the opposite.