For a home grow that you want to keep somewhat hidden... There are 3 size tents to look at. 2x2, 2x4, & 3x3. Now the 2x2 takes up the least space, will be the cheapest to set up and cheapest to run. It will also be the easiest to hide you can also find a lot of really affordable high quality lights to cover this space. But the big downfall in my mind is you can run 1 maybe 2 plants in a 2x2 which doesn't allow for much variety.
A 2x4 is going to be twice the space of a 2x2... So you can grow a better variety. It is only 2ft deep so you can easily access everything in the tent from the main door. It still sits tight against a wall. I really like a 2x4 tent. For me the biggest drawback is it is harder to find a light to fill the footprint. Yes you can get a lot of good lights for a 2x4 but if you want a good quality bar style light... You are almost better off to buy 2 lights for a 2x2.
The 3x3 sits a little further away from the wall... And it's not quite as easy to access the back of the tent as a 2x2 or 2x4 but it's doable. The benefits of a 3x3 is a much wider choice of lights and there is 1 more square foot of space than a 2x4. I think you usually get a little more head space than a 2x2 or 4x4 also.