I have a G23 I've been carrying a few months ever since I switched from my M&P 40c. I don't have a baby glock (26 or 27) but the M&P 40c is pretty comparable as far as grip goes.
I found that, for myself, the little bit of grip missing in the palm of my hand made the smaller gun a little uncomfortable to grip and shoot. So I switched to the G23 and think its perfect for me, I get a full grip and the difference in size makes literally NO difference in concealing. I found out that a full grip was way more important than a little more (not really) concealablitity, but that's me. If you can conceal a 26, don't really see it being that different to conceal a 19, but again thats for myself.
Your doing the best by going and shooting both and finding out what works best for yourself. Take your time and really try to get a feel for each. Post back and let us know how it went.
I previously owned a Glock 27 (.40 version of the 26). I ended up selling it in favor of the Glock 19. The 19 allows all my fingers on the grip and is easier for me to operate. I also use it as my primary handgun when I take training classes. The subcompact Glock was fine but just didn't fit my hand well. I was more willing to compromise on concealment than ergonomic fit. As a bonus, the 19 holds 15 rounds in the mag.