Having said that, I prefer the Springfield line for a few reasons:
1. I dislike the Glock grip angle. They don't point naturally for me.
2. XD/m/s magazines are steel instead of polymer. That allows the grip to be a little slimmer.
3. Glock uses polygonal rifling which can be troublesome for cast bullets (which I use almost exclusively).
Both are fantastic and I would be happy with either of them. I typically lean towards Glock. Both shoot real smooth. I used to be strictly Springfield. But one day I happened to pick up a Glock and never looked back. Still have a XD-s, but it is not my "go to."
I switched from an XD 9mm full size to a Glock 17 because I started having issues with the XD slide not locking back on an empty magazine and I once when I was shooting it was knocked off of the bench into the dirt and had a small pebble get lodged into the grip safety that took me forever to get out and pretty much disabled the gun until I did.
Both are great guns. It's like asking if Ford or Chevy is better.
Either one should be a solid, reliable gun. Given that the operating system and controls are the same, they are practically two versions of essentially the same gun. I love my XD, but a glock is easier to conceal, if that's important to you. The slide on the XD is pretty tall and blocky, which makes it a little harder to hide.
I own and like both! However, if you are planning on ever modifying your handgun, or buying more mags then I'd recommend the glock. Parts and mags are cheap and Available all over for the glock! Xdm mags are expensive and modifying them are expensive and difficult.
Since its opinion only...not subkect to which is "better", I say Glock for me. NOT because I am a fanboy...in fact I hate quite a few Glock models for various reasons...but I do like my G19 Gen4. Had an XD only once...got rid of it quickly because I just didnt ever really like it. I tried to like it, to no avail.
Strictly a personal preference here, but I have owned the XD's and do own Glocks, and I have to go with the Glock...specifically the G19. I shoot that steep Glock grip angle the best.
I prefer my XD over my G17 as far as preference goes, may depend on what you want to do with it & how versatile you want it to be.
The Glocks are supported far more by the aftermarket for accessories & such as well as KelTec sub2k having a glock magazine option, wish they had an XD mag option.
I love my XDm. It feels great in my hand and when Im not being an idiot, it's incredibly accurate. In all fairness, I've never shot a G19. I've never had too, my XDm has always been fantastic.
Of course the biggest factors are how well you shoot each and reliability. I feel comfortable saying that both are reliable.
On the Glock side they all have the same basic look and feel. It is just a matter of proportions, caliber and Gen 3 or 4 in their double stack lineup. Of course Glock also offers single stack models with the 42 and 43.
The Springfields do have more variations with the XD, XDSC, XD Mod 2 and XDm in the double stack arena. And of course they off single stack models too with their XDs lineup. With the double stacks, it really is a matter of personal preference. And I would advise you to check out the grip on all of them if you're considering the Springfield route.
I personally have 2 XDm Compacts, 9mm and .45 ACP. I love the way they feel and shoot. But I was not particularly fond of the stock trigger. I replaced the triggers on both myself with the Powder River Precision Drop-in Trigger Kits. It took less than 30 minutes following a Youtube video, even being meticulous about it. The difference with stock vs upgraded trigger is night and day and I highly recommend the PRP triggers for Springer polymers. The kits are specific by model and available for all the XD lineup with exception of the XDs. This brings me to the next point. I also have an XDs 3.3" in 9mm. PRP does offer a Spring & Sear Kit for this model that does lighten the trigger and make it a little smoother. But it doesn't do anything for the travel or reset. I like all 3 of them. And I rotate the XDm Compact .45 ACP, XDS 9mm and SIG P238 for carry, depending on my outfit for the day. My daughter laid claim to the XDm Compact 9mm. Being a bigger guy, I also have bigger hands. I normally carry with the compact magazines fitted with Pearce Grip Extensions on my Springers. For the SIG P238, I carry with the Extended Magazine. That gun is for pocket carry when I'm out in casual business attire.
While I have handled and shot a couple in the XD line, I have shot Glocks since the early 90's, so I stick with those. I did find a 5" XD with an olive frame, but did not have adjustable sights. I can't find it on the Springer website, but it felt and handled great.
I would urge you to rent and shoot both. That will tell you pretty quick which one works for you.
I'm not a Glock fanboy by any stretch but I'd go Glock in this case if nothing more than accessory/part availability and ease of repair. XD's are nice but I know of no police department that issues them and have heard of small parts breakage when they're run hard. Not an issue for most people however.