I’ve not done any yet for 6mm WW2, but the plan is to do multiples of 75mm squares. These are for Rommel however, so the area of any town will be clearly delineated by the grid. What it means is that a square in Rommel can be filled with buildings, but if the town is occupied, some bases can be removed so the figures can go in the square.
For 6mm Samurai, I’ve done 10cm square bases to fit a 10cm grid for games. These will be essentially impassable terrain so there’s no need to have smaller bases. This has meant that more detail can be put into the bases.
So, the short answer is that it depends on your rules and the type of game(s) you’re doing. Larger bases will likely be more aesthetically pleasing, smaller bases will have greater utility. A mix of both might be the best approach.
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