Growing hydro or soil doesn't effect the potency. That's pre-determined in the strain you get, and the different phenotypes for said strain. Although, you could screw up the grow and lower the potency of your plant by other variables. Hydro has faster vegging times, but the flowering time will remain the same. IE a plant vegged three weeks in hydro will be bigger than one vegged in soil. I prefer soil, as it is more convenient for me and my situation.
i recently switched from soil to hydro with (knock on wood) fantastic results so farrrrr. but who knows
Hydro is more labor intensive, soil is more forgiving. If this is your first grow soil might be best to start.
You can get bigger buds faster with hydro than with soil. Alot of people say that you can taste the chemicals from hydro but I think that if you flush properly then you wont have this problem. Soil is more forgiving and not so much mantinence (sorry cant spell right now HIGH AS A KITE). The point of hydro is to get your strains potential faster ( I think). From some people I have heard that hydro will make your plants grow bigger period but that is all hearsay. Just a noob though, passing on what everyone has told me and what I have read. Later dude.