In general, for an officer, combat arms, specifically Infantry is the best path to US Army Special Forces. You cannot replicate the infantry experience in any of the other branches. Although there are officers representing other branches that will make it through the Special Forces Officer Qualification Course, the learning curve is steeper and the transition more challenging. The core Special Forces mission is Unconventional Warfare, basically teaching, leading and executing infantry tactics with indigenous forces. If you have never served in the Infantry, you will have a hard time envisioning the whole spectrum of what you are doing. Of course there are exceptions. I don't think most experienced Green Beret Officers would argue with any of this. That all being said, if you have the desire, drive and will power, you can do just about anything you put your mind to even if it is harder for you than the guy next to you. Practice doing more than you think you can do, being in awkward situations and pushing yourself is the best guidance. Be physically fit and comfortable with a 50 lbs ruck for up to 25 miles. Finally, a comment about SEALs, SEALs are not Green Berets. Although they are cut from a similar cloth as Green Berets, their missions are different and they are selected differently. There is a reason you cannot commission directly into US Army Special Forces, the spectrum of missions are generally more complex for Green Berets than for SEALs. These generalizations don't apply to Special Mission Units. Good luck!