Frankly, any of the three should serve you well.
When carrying, for me, it is usually a Glock 26. I have owned several Glocks, and all have been about as reliable and simple as a handgun gets. Accurate as well, thru many tens of thousands of rounds. Thing to remember with Glocks is, pull the trigger, they go bang. Period. So safe gun handling and carrying is a must with these weapons. Simple really, just don't put your finger on the trigger until you are ready to fire, and use a good holster that retains its shape, and covers the trigger.
Shot quite a few of the Springfield XD series pistols, though I don't own one. They have seemed to me to be well made and reliable, just never really warmed to them I guess, as I am so used to my Glocks. Most models do come with an accessory pack which includes extra magazines, a holster and mag carrier, and a nice hard case.
I have no experience with the Ruger SR series, though I do have a ton of experience with the P series, as it was a common gun in use by several federal law enforcement agencies when I was a firearms instructor at FLETC. The Rugers in general are well built and reliable. I have seen more problems with some of the "elite" brands at times. If there is one weak spot with the Rugers, it seems to be the magazines, at least in the P series, as guys were always stepping on them during training, and bending feed lips, though probably not an issue for most people.
Another gun to consider might be the S&W M&P series autos. I have one, the 45 acp compact version, and am impressed with the grip feel, as well as over all performance. Seem to be carrying it more and more.
In the end, what really matters is what feels good in your hand. Handle each model, and note how they point, their manual of operations, sight picture, and over all feel. There are really no bad choices in the bunch.
Make sure you know the laws pertaining to self defense in your area, then spend a lot of time at the range putting bullets down range. A good self defense training course helps a lot with new shooters, and reinforces proper technique and mind set.
Larry