titandogg, First things first. How much experience do you have firing or using a gun. It is not hard but there are some important factors that need to be discussed and points of interest / precepts that need to be covered. You are jumping into the deep end of the pool with apparently little instruction or knowledge of how to swim. I would suggest that you seek out some training or help from a friend that already shoots. Try out different guns, different calibres and such. Now with that said; you ask an opinion about a 4" and 5" Springfield XD45. I have a son that has a 4" or the Service model. I have not had the opportunity to fire it yet, but it is to me, a very natural pointing handgun but so is my Glock model 21. I have great confidence in my Glock and from what I can tell about handling and reading of the XD, it too, I'm sure is a fine weapon. Let me say here that I carry my Glock so I'm quite familar with it. The 5" model XD woujld offer some advantages over the 4" but again, if you're not an experienced shooter, I doubt that you will know any difference at least for a while. The additional front end weight will indeed soften the recoil some, the extra inch will give perhaps in the neighborhood of 50fps increase in muzzle velocity; most of all the increase in the distance between the front and rear sight, the sight radius, could improve the percieved accruacy. That is the result of the longer distance between the two points making precise allignment on the target a bit tighter or easier. Back to trhe subject of recoil. I can tell you that the recoil of my Glock is, to me, mild with more of a stout push compared to say a snub nose .357 which can be a fire breathing dragon. Are you going to conceal carry your gun? If so definitly get some training, GET THAT PERMIT AND DO NOT CARRY THAT GUN UNTIL YOU DO! Also you may find, that for you, neither one of the pieces conceal very well. There is a lot to consider here. Do not let a gun store clerk tell you that this is the puppy for you. He can not possibly make that call. He can make suggestions but the decission is for you to carefully make. I trust I have not scared you away but give you some things to think about. OH, if I were going out tomorrow to purchase an XD, I would want to handle the 5" and it pointed like my sons 4" and I believe that it would. I would buy the 5".
Regards Pistol Toter