19 or 17
I'd go with the 19 for the following reasons:
1. Controllability. The difference in practical accuracy and controllability between the 17 and 19 is extremely small (for me). I actually prefer the 19 because it seems to balance better in my hand, as opposed to the 17, which balances slightly further forward. Because of the 17's longer slide, it should give you faster recovery on follow-up shots in double-tap and other rapid fire drills. In practice, however, I've found that the compact is just as fast as the full-size model. As far as accuracy goes, I've never noticed a substantial difference despite the 17's slightly longer sight radius -- I actually shoot the compact models better because of their balance.
2. Concealability. The 19 wins because of its slightly shorter grip. You will probably carry IWB, so muzzle length between the 17 and 19 is less important. (If you carry outside the waistband, the 17's muzzle may peak out under your covering garments, so the 19 wins.) Back to the grip ....... it tends to be the hardest part of a firearm to conceal. I'd opt for the 19 because of it's slightly smaller grip. Also, if you carry on your strong-side hip the 17's extra grip length will make a difference when it keeps rubbing against the back of your seat and putting pressure on your belt and side. Uncomfortable.
3. Capacity. Everything's a compromise. I wouldn't worry about giving up the two rounds. 15 is plenty. If you carry spare mags, carry full length 17 mags.
4. Storage. Even if you carry your Glock with you, you may have to remove it occasionally at banks, hospitals, court buildings, etc. The 19 is smaller and easier to tuck away than a 17. For example, I have no space under my seat 'cause it's filled with car gadgets .......... the 19 will go places where the 17 won't. Maybe not a concern for you.
I carried a 23 for a number of years and selected it instead of the 22 for the above reasons ..........