Bigger is better.

In hydro you worry more about the root ball. You need to figure how big you want the plants to finish and then select the net pot accordingly. For SOG grows the 3 3/4" net pots are about as small as you want to grow. The plants finish less than 30" and do just fine. For a DWC you want more of an 8" net pot and the plant can grow up to around 48-60" tall at finish.

There is no chart that I know of but experience tells me those sizes work.

Is that want you are talking about?