So I go to the range the other day with several of my favorite guns. At the time, there are only a couple other folks on the line so I take out my SW 686+. As soon as I start shooting, the place fills up including the stalls on either side of me. Immediately, I start getting "the look". I only brought .357 rounds with me, so in the interest of getting along with my neighbors, I pack up the Smith and Wesson.
Next, I take out a couple quieter HK P7s. If you've fired these 9mms, you know you're going to have a ton of fun, but not for too long as they heat up rather quickly. Before too long, in the interest of preventing third degree burns to my hands, I pack up the Heckler and Kochs.
Finally, I take out my HK45. So I start shooting, and shooting, and shooting. Go out, drink some water, buy some more ammo, and then go back in for more shooting, and shooting, and shooting.
Overall, I was in the range for about an hour and half. I figured it out and I shot about $24 in .357Mag, $22 in 9mm,
and over $200 in .45acp! Ouch!! (Most of this was WWB) That HK45 (read XD45) was just so darn fun to shoot! (Plus the gun is still fairly new and I wanted to give it a good wringing out.)
Take this story for what it's worth. My humble opinion is that if this is to be your ONLY gun, you're going to practice a lot with it. At least you should. There are currently outstanding defensive 9mm rounds on the market. Your XD9, if anything like mine, will eat everything.
Buy the 9 in the XDm, and start saving up for when SA finally releases the XDm in 45.
Good luck and happy shooting!