Well, with me being a huge GLOCK fan for pure ease of use and simplicity of design, a firearm that you can count on that just plain works, I have to say, the XDS is actually a fine pistol, fit and finish is great ergo's are good, even though the firearms design is targeted to slimness for conceal carry. The XDS has a couple of nice features a GLOCK doesn't. Price wise I believe they are about the same.
With that being said Ive owned multiple GLOCKs and pretty much adapted to them. I can shoot them all acuratley, no matter the size or caliber. Considering they pretty much are all the same pistol with different dimensions.
Unless your debating between a G36 and XDS the only real arguing factors would be compairing a XDS to any other GLOCK would be a discussion over ammunition capacity.
How many rounds do YOU feel comfortable in carrying? Off topic but I remember one time I was in a situation where I almost had to pull and possibly use my G19 and as odd as it may sound the thought cross my mind of, is this 9mm going to stop this quick enough? Meaning in a split second it crossed my mind that it was highly possible he could have squeezed off a few rounds into me as I was doing the same to him with my 9mm.
That event led me to purchasing a G27 even though I really wanted something chambered in .45 (should have gotten a G36) My experiences with the G27 wasn't so great (you can include the G26 into this as well because I have owned both). I loved to shoot them, because I was able to do it accurately and GLOCKs just felt good in my hand. The G27 recoil was pleasant as well. The only problem I had was the bulkiness of the pistol. I actually remember a few years ago asking GLOCK why arent you guys redesigning the G26 and G27 with single stack mags and slimming them down a bit!? You know if they were to do that now (come out with a slim line G27 and G26) there sales would jump up again, and would find themselves in the whole CCW slimline craze. Conceal carry hot topic right now and most are looking for something that's effective and keyword "concealable and comfortable" not to say the G26/27 cannot be conceal easily.
From my experiences though the G26/27 was not a suitable conceal carry option for me even though I loved them both "equally"
Ok let me stop rambling and get to the key points here. The G26/27 have very short barrels and very short grips. Perfect right? that's what we need to meet our conceal carry or backup needs a small gun. Well I noticed that the thickness of the firearm did not complement these features, what I found was a pistol that was clunky on the hip didnt tuck away nicely and was hard to get a positive, proper hold on the grip when carrying IWB. (Which is a conceal carry option that is used more commonly) I personally feel the G23/19 are far better options for CCW over the G27/26. The slightly longer barrel is a plus for both accuracy and "tuckabaility". The just so slightly longer not
larger grip allows a more positive hold or purchase, not to mention the added capacity you get going with the G23/19 over the G27/26.
Now if your a LEO and your primary is a G22 and your back up is a G27 in this case this is a ideal CC option, and GLOCK is targeted for LE and MIL use. So in these two category's GLOCK is the way to go. As far as the civilian CC population goes, small, slim, lightweight and effective is what everyone is looking for nowadays and ammo capacity is not much of a make it or break it kind of mentality considering study's have shown in most self defense scenarios the defendant usually only uses a few rounds I think the ball park lies somewhere in between 2-5 shots to end a engagement.
Now we all know it always breaks down to personal preference and everyone has their own view points, and want and needs. I found in my case the XDS was the way to go for now, and I hope it serves me well.
The G30S was my initial choice but when I put the XDS in my hand I bought it. Dont get me wrong I will still be purchasing a G30S
I dont know if it is in the works or not with GLOCK being more focused on LE and MIL sales, but if they were to release a G27/26S I think we all know where the sales would go.
To name off a few decent CC options I would recommend..
SF XDS, G36/G30S, SigP938/P238, KC PF9/P3AT, Ruger LC9/LCP, S&W442, S&W BG, KAHR PM9/P380, S&W Shield 9/40, Baretta Nano, NAA Guardian.
These are just a few but keep in mind study's have shown firearms chambered in calibers .45 and .357 are most effective in SD situations. Which is funny because a lot of people carry a .32 and are just fine with that and that's to include myself. Some days a .45 is just not, I wont say practical but reasonable. Like i said before its all personal preference and the Who, What, When, and Where really are the decision factors when carrying conceal carry pistols. If your a daily CC personnel than I think its important to have variety in your CC options.
Hope this was of some help.
-No expert, just a average joe throwing in my 2 cents.