1st off, anybody who tells you HK does not support their product is full of it. They are most likely fanboys of another company and have little to no real experience with HK or the top level service you'll get from them. I should know; I was once one of those fanboys. I have nothing but the HIGHEST praise for what those CS guys at HK do. You will find 95% of this forum posts will vouch for that.
Secondly, since you named the Glock 23 I'll assume you are considering .40 caliber? Although I am uncertain of why you narrowed you search to Glock 23 vs. P2000SK, since one is a compact, the other a subcompact. A more balanced comparison would be the Glock 27 to the P2000SK or the Glock 23 to the P2000, or P30. Either way, your call, but sticking to the caliber observation the modern HK pistols were designed specifically to the .40 and scaled down to the 9mm. Yes, you read that right. It was built for the .40, and scaled down to suit those that need/want 9mm. Glock, Sig, heck EVERYONE else built .40 pistols on 9mm frames, and often times the guns are not suited to that caliber and have had years of tweaks and design changes to suit the more powerful cartridge. Also on the caliber topic is the fact that Glock barrels are not fully case supported. There is a small portion of the rear of the case that has no support from the barrel. In the case of the .40 that is bad. Many instances of that caliber have blown clear through the cartridge wall in Glocks for that reason. And for that reason Glock has had to reinforce their chamber design more than once to accommodate the hotter defensive loads found today. More importantly you will find that ammunition manufacturers have actually redesigned the case of the rear of the .40 to reinforce it against those instances when using the hotter loads in a pistol that is not fully case supported. Basically since Glock undercuts other manufactures so much ammo makers had to fix their problem for them since so many LE agencies use the Glock. These facts are why I do not own a Glock .40. .45 and 9mm yes, but never a .40.
Lastly striker vs. hammer. I can't help you there. Even in the HK world you'll find those who swear by DA/SA, and those who defend the LEM trigger against all others. I personally have become an LEM convert, and it gives you something of a striker feel in that each trigger pull is the same. Being a Glock convert I find it better suits my trigger muscle memory better than the traditional DA/SA pistols.
Good luck on your hunt, and mark my words; you can find a decently priced HK P2000 or P2000SK for a cost differential that is nominal at best when compared to Glocks. It never ceases to amaze me how people will pay $30,000 for a car knowing full well they MIGHT have it 5 years and scoff at the notion of paying over $600 for a weapon that will last them their entire lives. Especially considering that you may very well depend on it to save that life.