I have heard that it is better to have a shorter cycle for your plants because when they are smaller the nugs are more potent then compared to a larder plant I just want to know if this is true or not.
Not true at all. Vegging has nothing to do with the potencey or overall production of your buds, the larger the plant the more you will yeild in theory however. A plant does have a limit though, the taller the plant, the more branches it is going to have, and therefor the more budsites it is going to have. In saying this though, a plant can only be pushed so far, just becuase a plant is 20 feet tall does mean its going to yeild pounds upon pounds. Their are also other things to take into concideration, when growing both indoors and out the taller the plant is, the less light the lower branches are going to get which is going to cause the bud toward the lower branches to become not as dense and developed as the budsites towards the top. To answer your question in short though, no vegging your plant for a month, or 5 months has no effect on the potency of the bud it produces, thats what flowering is for.
I agree with all of this with a couple of exceptions: LST, SOG and SCROG change the rules on this. Change "tall" to "large" and I agree with you 100%. In many and maybe even most cases this may be true but not all. If an indoor grow is not over stuffed and has the right lighting you can get nice buds all around.