Which is best????

I've read a lot about using dehumidifiers as they help the leaves become thinner with more resin as the leaf thinks it is drying out. However in these forums there has been alot of talk about using humidifiers in their grow rooms to help keep moisture levels up.

Which is best??

Welcome to the forum Jimbo. Where did you READ something as stupid as that. The only reason you would use a dehumidifier is if your humidity level stay above 55% constantly. Intelligent people would try ventilation to solve this problem first.
IF the humidity level gets too low the Stomata , which are on the bottom of the leaves, will close up to keep moisture in the plant. When this happens, the plants will build up toxins that would normally be expelled.
A humidity level around 50-55% would be ideal for healthy growth.

Proper humidity levels are as follows, around 70% for early seedling development, 55-70% during veg and 30-40% during flower.
Peace

^^as video said but it isn't to bad if you just keep it between 40-60 in veg if you done the seeding in a dome in flower the humidity should really go below 50% to prevent mold in the buds to grow and force them to grow a bigger haze layer