I've done both, it's not entirely necessary from what I've seen but it might help a little. They were just fine in 6" square pots, 1.5 or 2 gal I think. They DO benefit quite a bit from LST though, I can tell you that at least.

Pic 1 - 3 plants, 1 in 9.5" (3gal) pot, 2 in 6". Plant in 9.5" is 20 days ahead of others
Pic 2 - one of the plants in 6" pot at harvest
Pic 3 - plant in 9.5", heavy LST, at harvest.