In my opinion, if you are looking at their subcompacts and hoping for something like a Shield or even a Glock 26, like you said, you are going to be disappointed with the size.
If I am going to compare them to Glocks, I think the "SK" line would actually be somewhere between the subcompact and compact line, as far as size goes. The fact is that HK handguns, at least the ones based of the USP, have always run a little bit on the larger side. I know this may be a negative thing for many, if not most people, especially when looking for a gun that is a dedicated CCW.
I have to say though, personally, as someone who has always been in the compact to full sized arena as far as handguns go, but just wanted something a little bit smaller and lighter than what I was carrying, the "subcompact" HKs are the perfect size. But like I said, I can see how some may consider them too large for what they are.