Hey Jose, I just got your email. Hopefully this will help.
In simple, to-the-point language, the difference between long travel, and standard travel is pretty simple. They move the lower shock mount further out toward the spindle for a longer shock, and charge twice as much for the arm. Often times they add an upward bend in a specific place on the lower a-arm to accommodate for the longer shock, as well as to change the angle of the ball joint or heim to avoid binding during articulation.
Depending on how aggressive of terrain you are riding, you might want to consider long-travel. Standard travel aftermarket a-arms WILL increase your wheel travel, simply because they move your wheel further out from the pivot point.
The above, is called the "fulcrum effect". Imagine you have a teeter totter where the fulcrum (pivot) is 4 feet off the ground. One end of the teeter totter is 8 feet long (+3 a-arms), the other is 4 feet long (stock a-arms). Which end of the teeter totter will go up higher when the opposite end is pushed down?Also, which end will take more load to push down? The longer the arm, the more leverage, therefore the easier it will compress your shock. Often times, people will attribute their quad "lowering" after installing +2, or +3 arms, but in reality, the cause of the problem is simply more leverage on their shock.
I spent about an hour doing up a bitchen illustration to explain my point, but I just fucking deleted it on accident... FML.... Oh well. Hopefully this answers your question.
Synopses: Longer arms for stock length shocks, WILL increase wheel travel, but not to the extent that long travel arms will.