I don't have the subcompact version of these so grain of salt, but with GLOCK I got a better value vs. H.K. as GLOCK is I.M.O. also top quality and for less money if you are comfortable with it. However I personally don't like carrying the striker fired "safe-action" so I generally stick with D.A./S.A. Sig and H.K.
Finish quality my H.K.'s finish already looks worse than that of my GLOCK which actually has more years and rounds on it yet still looks brand new. The GLOCK also has a faster trigger and shorter reset though the H.K.'s is fast enough when you get used to how to shoot it. Also, size & weight vs. capacity ratios are always better with GLOCK. Really, the H.K. is 2nd place to almost everything except grip angle and comfort of the grip contour for me once you find the right P2000 backstrap. Also, the H.K. is a little nicer in random details like their slides feel smoother to rack, the mags don't just drop-free but it springs them out with force, and all the controls click more securely and feels nicer, if that kind of detail matters to you.
Good thing is you picked two of the best right there and you can't go wrong with either. Both will be reliable and accurate. Just figure out which grip angle and grip shape you prefer. Also my comfort level with GLOCK trigger puts me in the minority (I.E. not professional enough) so if you are comfortable with a relatively light and short trigger as most are I would get the 26 easily, but all this is J.M.O. and Y.M.M.V.
Oh yeah when you are in the gun-shop, you will feel a little like a dick for asking him to do this, but trying the different backstraps can make a world of difference. I have big hands, and for instance the P220 is a good fit to me so I was trying to duplicate the same "trigger reach" as that one, however with the H.K. the medium backstrap which was much smaller actually felt better and I naturally point it and control it better this way. Sometimes that can be surprising. Doesn't hurt to ask, though he might not want to let you try different sizes and I don't blame him. The upside is those swap-a-straps are in there solidly but doesn't just click in-and-out like some other brands' design, overall a good design because I was anti this idea until the P2000 it is so well done you don't even notice it's puzzle piece desing there until you look close, defintely cant feel it.
Good luck
Oh
For my H&K owners that also own Glocks, how can you justify paying the premium?
For me it was somewhat of a splurge, so I can't objectivly justify it feature vs. feature like I can with a GLOCK (I.E. most everyone prefers a better finish and saving money etc), excpet from a personal preference standpoint. But you CAN say if not better quality then nicer (like the smoother details above I mentioned), but yes I do admit the GLOCK is a much better buy.
Is the H&K P2000SK more accurate than the Glock 26?
No. You're likely to find more differnce even within one model than consistently between examples of these two(I.E. they are both really accurate probably equally averaging a dozen of each).
Is the gun really worth it?
To me it was, because for my preferences it uniquely filled my needs. I admit it was somewhat overpriced but still worth it to me if that doesn't sound hypocritical. The only other alternatives I found features specs size etc I found were the likes of Ruger and Taurus of which I've had a few and I prefer Sig, GLOCK and H.K. It's the whole point of limiting returns I think, the lower you go the better value you get (E.G. even Hi-Points are accurate and reliable) so you end up paying more than you should for each step up. Ask the Ed Brown 1911 guys if they are overpriced, they'll say yeah but worth it. Granted those are guaranteed accuracy at 50 yards etc so you do pay for that, just an analogy and I'd buy some of those if I were rich. Let us know what you decide, or get both L.O.L. now and sell one later if need be. You'll want to keep both. After buying several brands, GLOCK sig and H.K. are the only ones I can't make myself sell even though I don't really NEED them.