I said XD 4" Service length. I stumbled upon my XD V-10 4" in 9mm and I am sure glad I did. It has been one of the most reliable and fun to shoot guns that I own. I have more rounds through my XD than any other gun I've ever shot, with the exception of an old Marlin bolt gun .22 LR.
To me, XD's and Glocks and probably M&P's are just excellent lego-type guns that you can build up or simply leave alone and shoot as is.
But as far as my XD is concerned, the sucker just runs! Yes, I've had some failure here and there. I've blown a barrel out. I've worn my guide rod out. But these are not really the gun's fault. It's just part of use. I've got spare return springs, guide rods, spare barrel, tons of spare mags, multiple holsters, and I even bought my dad one.
For me, XD's point well and feel good in hand. The grip angle is more natural than a Glock's. Also, the non-factory trigger I have in my XD is awesome. But that is where I'd stop the comparison with the big guys, Glock and M&P's, because all of them can likely have good triggers. Glock triggers out of box are just slightly nicer and more predictable than XD triggers. But, if you are a nutter like me, you are going to replace or modify the trigger anyway on any of the three brands.
If you are looking at XD's, I'd steer you towards the 5" model for the longer sight radius, but it all depends on what you do with the gun. I think a lot of people tend to buy full sized handguns intending to conceal them, but I'd steer you away from this type of thinking. To me, full-sized handguns are the guns you learn to shoot with, then you can learn to shoot and conceal a compact handgun. If you agree with this logic, then you may as well get a 5" gun (or the respective longslides from Glock and M&P) because it will simply be easier to learn to shoot on a bigger gun with a longer sight radius. Also, I feel like if a gun is a better or more capable shooter it is simply more fun to shoot.
I'd say buy a XD 4"/5" in 9mm, then get an XDS in 9mm to carry. You learn to shoot on the XD standard gun, then carry the XDS. A 4" XDS would make a decent gun to learn on as well, but I don't know your expectations you have for a firearm. The trigger on stock XDS seem better than stock XD's. And they have upgraded sights fiber optic sights, too. The biggest drawback to getting an XDS instead of an XD is that you will lose round-count, but it isn't a draw-back if your primary reason to own a fire-arm is concealing. An XD might get left at home, where an XDS will (for me and many others) be more likely to make it into your every day carry.
Finally, XDS's are really not bad to shoot in the recoil department. I've fired the 9mm and .45 ACP versions and neither are bad. But, a XD 5" would likely be easier to learn on even so.
Also, there's my personal favorite, the XD 4" V-10 model. It comes with two rows of 5 holes cut into a "V" at the top of the barrel and through the slide. If you can get past the pressure and blast created by the porting, you will come to appreciate the lack of recoil.
M&P's have 5" ported guns that look pretty awesome, and G34's have open-top slides that you can drop a ported barrel into. I have a sickness; I know.
OH, XD(m)'s have good track records, design, and even a 5.25" gun with upgraded sights. Also, a good choice.
