Way too big. Huge waste of medium and nutrients in my opinion. I veg for 8 weeks and never use anything larger than 3 gallon for my indoor plants. You can grow huge plants in very small pots, it just means you have to water/feed more often. In my 3 gallon pots, in week 5 of flower, I only have to give my plants a gallon of fertilizer every second or third day.
I'm not saying that 3 gallon will work for everyone, but over 8 years of indoor cannabis growing, I've found the 3 gal to be the very happy medium.