building a grow room

im building a room i have just about all i need. i have 2 grow tents a6x6x6 and a smaller one i have all the light i need and ventilation and air in. should i use both tents or just grow in a big room

If you already have all of the lighting, ventilation and space needed for both tents, go ahead and use the small one for vegging. You'll have vegged plants ready when the flowering tent is harvested.