First handgun purchase?

With the vast improvements in 9mm ammo technology, the 40 doesn't make much sense.

Why not learn to walk before running? Your first pistol should be a 22 target pistol. Here is a simple comparison - 22 ammo is $23 for a box of 500. 45 ammo is $39 box of 50. When you consider that what you learn with a 22 pistol is directly useful with a bigger pistol - starting with a 22 makes more sense. For $100 in ammo you can fire 2,000 rounds over a summer and be a really good shot in a few moths. Or, you can buy 150rds of 45 and fire it in one afternoon and still be a lousy shot. By the end of the summer, to be a decent shot with a 45 you would have wasted $700+ in 45 ammo.

Get a 22 target pistol the S&W 22A. Learn to be a decent marksman. Learn how to control your trigger finger, breathing, and how to hold and fire a gun properly. Once you get the hang of it - then go out and start looking at the centerfire pistols. There is a reason they make Glocks, Sigs, S&W, and XD's that all look alike - because they feel different....... and you really need to one that feel correct in your hand. Smart people - get trigger time on all these different models before putting any $$ out.

How stupid do you think you will look and feel after buying a Glock, firing $700 in ammo only to discover the gun doesn't fit great and you can't hit crap with it....... but you do 200 times better with a Sig or XD? Now you will have to sell the Glock - loose your shirt on the sale - then pony up the big $$ for a better fitting gun. And you are still out that initial $700 in ammo.

Learn to walk before you run. Get a nice target 22 and move on from there.

Get the Glock 19. The problems with reloading and pressures with the 23 in .40 far outweigh the advantages, especially with, as CTM has stated, the significant improvements in the 9mm and modern projectile designs.

If you are going to get a Glock then get the Model 19.