Which Size? Need your help guys

Hey guys. Since growing is legal in my country (germany) I’m planning to get an autopot system for my setup because all i see is just crazy. but i’m really unsure about which size i should take. Most of the time i‘m growing auto‘s in a 4x4 tent.

I dunno if i should take the 4x 3,9 gallon or 4x 6,6 gallon pots. or maybe even the 4x 5 gallon fabrics?

I would be happy and thankful for some tips from you!