The tablets would almost certainly have less mass and take up less volume than the equavilant amount of strawberries. Strawberries would either need to be frozen (requiring energy for refrigeration) or perhaps grown on the mission. However, there's always the possibility of the crop failing.

If the active ingredients could be put in tablet form, you might well be able to put the equivalent of a lot of strawberries into a single tablet. Remember, each additional kilogram of mass for consumables like this requires many additional kilograms of propellant over the full mission. Mass tends to snowball rapidly in space vehicles, and this is especially true for a long manned mission like one to Mars.