Your right, clones do need some time to root, but you can flower them after they've had just a day or two in their final pot to recover from the transplant shock. What it all comes down to is how much space you have, how many plants your growing, and how much light you have available for them. I personally like to veg my plants from anywhere between 1-2 months, and end up with big bushy plants that take up quite a bit of space. As Smiley noted, this method has it's drawbacks compared to a SOG grow like he does. I don't get to harvest as often (well, actually i do since I'm on a perpetual grow, but thats a different story), I can't fit nearly as many plants under each light, and it requires quite a bit of floor space (approx 16 sq ft for the 6 Ive got flowering currently). The payoff is that i get to harvest anywhere from 2-4 times as much as he does per plant.
When you get right down to it your overall results from growing a few big plants versus a lot of little plants aren't going to be all that different. What you have to decide is which is going to fit your grow area better, as well as your legal requirements. Remember, the more plants you get nailed with the longer the jail sentence if you get busted, and if your like me and live someplace where MMJ is legal you still have to worry about keeping under the plant count limits.