Regular Travel Arms simply means that the a-arms retain the same shock mounting locations as OEM, so you are able to use your stock shocks. This is a popular option for riders who are not wanting to spend the extra money on aftermarket shocks, but still want a wider a-arm.
Long Travel means that the shock mounting location on the lower a-arm has been moved, giving you the ability to mount a longer, aftermarket shock. This is popular among cross country and motocross racers who need that extra travel for a better ride, giving them a competitive edge.
A common misconception about Regular Travel/Long Travel is that it affects the width of the a-arms, which is not the case.