If you take a cut from a plant that was started under 12/12 from seed you will normally need to put it back to veg before flowering it. Of course you can put it straight to 12/12 but the strain will dictate the result.
In example if you did that with Cheese you 'd end up with a mini sized plant so there wouldn't be any logic behind using this method..(no matter if there was any difference in flavor or potency).
Now..if you worked with a heavy sativa line like a haze dominant hybrid say Neville's Haze or a pure sativa things would be very different. The cut under 12/12 would take quite few weeks before it would start to really flower. Basically it would root then grow (veg) for several weeks before it would really start to flower no matter the lighting.
Thats the case with all sativas and 12/12 from seed. They basically grow/veg till they get mature enough to start flowering irrespective of lighting. They don't start to flower unless they have become hormonally mature and stored enough carbohydrates.
Another thing to mention is that with 12/12 from seed and any strain...any single day counts and is important as it will affect the end result. With no veg time one needs to grow the plants very well to have em reach their potential , while with vegged plants things are much more different and forgiving.
I haven't taken & flowered straight away cuts from plants that were in 12/12 (and were started with 12/12 from seed) so I can't compare how these would smoke compared to cuts from a more mature mother or a cut that was vegged few months.
But I have grown same cuts and plants from seed with zero veg time Vs some veg time and found no differences in flavor and potency.
It would be nice to hear what others think on this that have tried to do similar comparison tests in the past.
l33t