Depends on how long you want to veg them. Consider you have about a 4x4 area of good coverage under each lamp. You can fit at least 16 in smaller pots and veg for a short period of time or you can use the 5gal and fit about 8-10, vegging them longer. I've seen 50-60 clones done in plastic cups w/ no veg under 1 lamp, so it's really a personal preference.

Cannabis doesn't really like to be crowded and will grow bigger buds if given more space around the plant. However, total yield will be slightly more with high numbers of plants spaced closely together. But, that means more work and more trouble should you get pinched.

So, your choice. More and smaller, or less and bigger.