My final pots are 10 litre for the tall varieties but could probably do with going bigger as they become very top heavy and need watering twice a day in summer.

My Balconi toms go in a 3 litre.

we use 10l pots and as I sink them half way into the soil of th egreenhouse they seem to do well. I do stake the taller varieties as well to give that extra support and to make harvesting easier as I can see what is where.