imo, yeah you both need a strong smash. ex) when your serving, you serve at T, your partner usually at the back, when he serves hes at the T and your at the back. It would take too much time and stamina to keep switching positions after every serve. If you both had a strong smash you would have extra stamina and would have less on your mind so you could have more of an advantage and could focus more on the game rather then thinking about switching and running around after a serve, also during the transcition they could hit a drop which would probly put the person in the front that wants to switch to back staying there while the back person is.. well my fingers are tired so you can probly imagine what would happan.
Strong smashes come in useful only if you force your opponents to lift, or return shots high that are short of a good length. Look at the Indonesian Badminton Open men's doubles final-a match dominated by fighting for control of the net to force your opponents into playing high shots.
